British Prime Minister David Cameron came under intense pressure Saturday from stunned continental diplomats to begin the painful process of extracting his nation from the European Union, as political aftershocks rocked both sides of the English Channel following Britain’s historic vote to leave.

After a tumultuous Friday that saw world financial markets plummet and Cameron announce his intention to resign, British voters and their European peers began on Saturday to digest the full and enormous consequences of the historic decision to break with Europe. In Berlin, foreign ministers from the six original members of the E.U. spoke with one voice, effectively telling the British that now that they have decided, there should be no delay to the exit door.

Cameron has sought a looser timetable to give his Conservative Party a chance to choose his successor, whose task it would be to fashion a withdrawal deal over the course of two years. But technically, negotiations can’t start until Britain triggers the bloc’s Article 50 — the never-
before-used mechanism to leave it.

Cameron has given no indication of pulling that lever fast. But for European officials stung by the vote, patience was wearing thin.

In a stunning victory for the “leave" campaign, Britain has voted to exit the European Union. Here's what happens next. (Jason Aldag,Adam Taylor/The Washington Post)

“We start now,” French Foreign Minister Jean-Marc Ayrault told reporters in Berlin. “We must be clear. The British people have decided after an initiative that was taken by Mr. Cameron. That was, is his responsibility.”

At the same time, deep intrigue reminiscent of ancient European power plays using knights and swords instead of the ballot box swirled over the future of Scotland.

Scottish voters, unlike the English or Welsh, voted on Thursday to remain in the E.U. — and Scotland’s cabinet met in Edinburgh to consider its next steps. Nicola Sturgeon, Scotland’s first minister and leader of the Scottish National Party, confirmed that the party would begin efforts to seek a new vote on independence, a move that eventually could bring another wrenching change to an island nation that is now operating without a clear road map.

The “cabinet agreed that we will seek to enter into immediate discussions with the E.U. institutions and with other E.U. member states to explore all possible options to protect Scotland’s place in the E.U.,” Sturgeon said Saturday.

During Scotland’s referendum for independence from Britain in 2014 — which failed — E.U. officials were circumspect, saying at the time that Scotland would have to get in line with the likes of Serbia and others who also wanted to join their club. If that position changes swiftly into an opportunistically strong pledge of membership now, it could drive an even deeper wedge between England and the continent.

Yet already, some E.U. politicians have said that if Scotland extends a hand, the E.U. should take it — suggesting the potential tug of war ahead for Scottish loyalties between London and continental Europe.

Meet the European leaders hoping to cause the next Brexit

“If Scotland wants to be a member of the European Union as an independent country, then they are welcome,” said Manfred Weber, the chair of the European Parliament’s center-right European People’s Party and an ally of German Chancellor Angela Merkel. “But that’s up for them to decide. That shows that there are positive signals. Some people do want to be members of the European Union.”

Britain could undergo even further dismantling if the nationalists in Northern Ireland, which also voted to remain in the E.U., press ahead with their calls for a vote on Irish reunification. Signs at the main post office in Belfast warned all who entered that it had already run out of applications for passports from Ireland.

In the tumult, Jonathan Hill, Britain’s European commissioner, announced his resignation Saturday, citing his disappointment at the outcome of the referendum. His departure as Britain’s most senior official in Brussels was expected, but it nonetheless was another reminder of how the vote Thursday is quickly shrinking the country’s role in European affairs.

Britain’s leaders have sought to offer reassurances that the vote to leave, which carried by 52 percent to 48 percent, would be dealt with in a calm, orderly fashion. But behind the scenes in Britain on Saturday, there was a flurry of crazed political activity.

As Britons fretted over the consequences of their decision, a petition for a second referendum — considered a long shot for myriad reasons — garnered more than 2 million signatures.

Leading Conservative Party politicians began maneuvering to replace Cameron. Boris Johnson, the flamboyant former mayor of London and a leader of the “leave” campaign, is considered the favorite, but he is likely to face serious opposition.

Since the vote, Johnson also has urged a go-slow approach to negotiations to withdraw from the E.U. — a marked change from his stark anti-E.U. rhetoric during the campaign and perhaps a sign that those who had championed breaking with Europe were chastened by what now lies ahead.

The referendum has also roiled the opposition Labour Party, with its leader, Jeremy Corbyn, confronting an open revolt from those who say he failed to campaign hard enough to stay. Senior party members have filed a motion of no confidence, threatening to make him one more victim of the Brexit fallout.

But Corbyn signaled Saturday that he would not go without a fight. Asked by a reporter during an event in central London whether he would run again for party leader if there were new elections, he replied: “Yes, I’m here. Thank you.”

Cameron, in announcing his resignation, said that he would stay through the transition to a new government but that he did not think he should lead Britain as it charts its new course independent of the E.U., leaving that to the next prime minister, hopefully to be chosen by October.

However, pushing back against such a leisurely timeline were the top diplomats from Germany, France, Italy, the Netherlands, Belgium and Luxembourg, issuing a joint statement Saturday that called for a start of exit talks “as soon as possible.” Their fast meeting underscored the continental effort taking shape to prevent further disintegration of European unity in the wake of the British decision.

German Foreign Minister Frank-Walter Steinmeier echoed calls for quick talks, warning of the risks of a drawn-out quagmire.

“We understand and respect the result and understand that Great Britain now concentrates on Great Britain,” Steinmeier said. But, he added, “this process should begin as soon as possible, so that we don’t end up in a long stalemate but are able to concentrate on the future of Europe and work on it.”

Two camps appeared to be lining up, however. Some European diplomats were eager to hold Britain’s feet to the fire for leaving — seeking a tough deal that would dissuade other member states from seeking similar referendums to leave the bloc.

But Steinmeier, as well as Merkel, who will be instrumental in the exit talks, were, at least publicly, staking out a position that made Germany the adult in the room. Earlier Saturday, Steinmeier told Germany’s ZDF television that Europe should “not go looking for revenge.”

Speaking in Potsdam, Germany, Merkel sounded resolute but patient. “To be honest, it shouldn’t take forever,” she said of Britain’s exit. “But I wouldn’t fight over a short period of time.”

She added, “Great Britain has to say what kind of relations to the European Union it’s envisioning in the future, and then we, the 27 member states, need to decide to what extent we can fulfill these expectations and what is in our interest.”

The rounds of diplomacy were laying the groundwork for an E.U. leaders summit Tuesday, when the heads of the 28-nation bloc will convene to begin discussing what could be a highly messy, even ugly, British exit. The next day, the 27 national leaders excluding Cameron are scheduled to huddle.

Yet many leaders, including the key foreign ministers meeting Saturday, have also conceded that to some extent, the E.U. needs to offer a mea culpa. The union needs, they said, to respond to widespread public criticism and antipathy among European voters beyond Britain who think it has become too remote and has failed to deliver on key issues including migration, security and job growth.

For Europe, Steinmeier described the British vote as a wake-up call.

“It is apparent that Europe needs to deliver solutions the people are asking for,” he said.

Balz and Witte reported from London.