Former London mayor Boris Johnson, runaway bookmakers’ favourite to become Britain’s Prime Minister, abruptly pulled out of the race on Thursday in a shock announcement less than a week after leading the campaign to pull the country out of the EU.Mr. Johnson’s announcement, to audible gasps from a roomful of journalists and supporters, was the biggest political surprise since Prime Minister David Cameron quit on Friday, the morning after losing the referendum on British membership in the bloc. Mr. Johnson’s withdrawal makes Theresa May, the Interior Minister who backed Remain, the new favourite to succeed Mr. Cameron.

She announced her own candidacy earlier on Thursday, promising to deliver the EU withdrawal voters had demanded, despite having campaigned for the other side. “Brexit means Brexit,” she told a news conference. “The campaign was fought, the vote was held, turnout was high and the public gave their verdict. There must be no attempts to remain inside the EU, no attempts to rejoin it through the back door and no second referendum.”

Surprise decision

Mr. Johnson, whose support of the Leave cause was widely seen as delivering its victory, saw his bid suddenly crumble after his Brexit campaign ally, Justice Secretary Michael Gove, withdrew his backing and announced his own leadership bid.“I must tell you, my friends, you who have waited faithfully for the punchline of this speech, that having consulted colleagues and in view of the circumstances in Parliament, I have concluded that person cannot be me,” Mr. Johnson said at the news conference in a London luxury hotel.

Supporters in Parliament, who had gathered expecting to hear him formally announce his candidacy, were left stunned.Mr. Gove, a close friend of Mr. Cameron’s despite differences with the Prime Minister over Europe, had previously said he would back Mr. Johnson.But in an article in the Spectator magazine on Thursday, Mr. Gove wrote that he had come “reluctantly, to the conclusion that Boris cannot provide the leadership or build the team for the task ahead”.Conservative lawmakers said Mr. Johnson may have been undone by supporters of Mr. Cameron exacting revenge for his decision to defy the Prime Minister and back the Leave campaign.“He who lives by the sword, dies by the sword,” said one lawmaker, describing internal party conflict on condition of anonymity. The lawmaker told Reuters that Mr. Johnson had realised his bid would fail after lawmakers defected from his campaign overnight.

Divided party

Mr. Johnson became the latest political casualty of a civil war in the ruling party unleashed by Mr. Cameron’s decision to hold the referendum on membership in the EU, an issue that divided the Conservatives for decades and now divides the country.Mr. Johnson, known for a jokey public persona and a mop of unkempt blonde hair, became a popular national figure during eight years as London mayor, and used his charm to aid the Leave cause after deciding only late in the day to push for Brexit.Several leading Conservatives questioned whether Mr. Johnson had the gravitas to run tough talks to mend the broken relationship with the EU and drive the country’s future on the global stage.In an article in the Times newspaper, Ms. May took aim at Mr. Johnson’s persona by saying government was not “a game.”

‘Uncertainty to affect near-term growth outlook’

Uncertainty over Great Britain’s looming departure from the European Union will dampen near-term economic growth for the U.K. and the rest of Europe and affect output globally, a spokesman for the International Monetary Fund said on Thursday.IMF chief spokesman Gerry Rice told a regular news briefing that market movements following last week’s vote, including for currencies, “were large but not excessively disorderly.”Mr. Rice said central bankers should stand ready to act to add liquidity or reduce excess volatility if the uncertainty over Brexit threatens to further hurt global growth.

Three suspected Islamic State suicide bombers who killed 42 people and injured a further 239 in a gun and bomb attack at Istanbul airport this week were from Russia, Uzbekistan and Kyrgyzstan, a Turkish government official said on Thursday.The official gave no further details beyond confirming the attackers’ nationalities and declined to be named because details of the investigation have not yet been released. Investigators had been struggling to identify the bombers from their limited remains, officials said earlier.

“A medical team is working around the clock to conclude the identification process,” one of the officials said.The attack on Europe’s third-busiest airport was the deadliest in a series of suicide bombings in Turkey this year.The pro-government Yeni Safak newspaper said the Russian bomber was from Dagestan, which borders Chechnya, where Moscow has led two wars against separatists and religious militants since the Soviet Union collapsed in 1991.The Kyrgyz security service declined to comment, while the Uzbek security service could not immediately be reached.

Turkish police detained 13 people, three of them foreigners, in raids across Istanbul in connection with Tuesday night’s attack.Counter-terrorism teams led by police special forces launched simultaneous raids at 16 locations in the city, two officials told Reuters. Turkish authorities have said they believe Islamic State was behind the airport attack.Yeni Safak said the organiser of the attack was suspected to be a man called Akhmed Chatayev, of Chechen origin. Chatayev is identified on a United Nations sanctions list as a leader in Islamic State responsible for training Russian-speaking militants, and as wanted by Russian authorities.

The Hurriyet newspaper named one of the attackers as Osman Vadinov, also Chechen, and said he had come from Raqqa, the heart of Islamic State-controlled territory in Syria.Turkish officials did not confirm to Reuters that either Chatayev or Vadinov were part of the investigation.

Growing threats

Wars in neighbouring Syria and Iraq have fostered a home-grown Islamic State network blamed for a series of suicide bombings in Turkey, including two others this year targeting foreign tourists in the heart of Istanbul.Islamic State has established a self-declared caliphate on swathes of both Syria and Iraq and declared war on all non-Muslims plus Muslims who do not accept its ultra-hardline vision of Sunni Islam. It has claimed responsibility for similar bomb and gun attacks in Belgium and France in the past year.

Turkey, a member of the NATO military alliance and part of the U.S.-led coalition against Islamic State, has repeatedly fired back on the Sunni hardliners in recent months after rocket fire from northern Syria hit the border town of Kilis.In a sign of the growing threats to Turkey, U.S. defence sources said on Wednesday that Washington was moving towards permanently banning families from accompanying U.S. military and civilian personnel deployed in the country.Critics say Turkey woke up too late to the threat from Islamic State, focusing instead in the early part of the Syrian civil war on trying to oust President Bashar al-Assad, arguing there could be no peace without his departure.

Once a reluctant partner in the fight against Islamic State, Ankara adjusted its military rules of engagement this month to allow NATO allies to carry out more patrol flights along its border with Syria.It has also carried out repeated raids on suspected Islamic State safe houses in Turkey.Nine suspected militants, thought to have been in contact with Islamic State members in Syria, were detained in dawn raids in four districts of the Aegean coastal city of Izmir on Thursday, the state-run Anadolu news agency said.

It said they were accused of financing, recruiting and providing logistical support to the group.The military killed two suspected Islamic State members trying to enter Turkey illegally at the weekend, security sources said on Thursday.One of the suspects, a Syrian national, was thought to have been plotting a suicide bomb attack in either the capital Ankara or the southern province of Adana, home to Incirlik, a major base used by U.S. and Turkish forces through which some coalition air strikes against Islamic State are carried out.