Leaders congratulate Cameron on win
World leaders queued up to congratulate David Cameron on his election victory, but amid the felicitations there were also hints of challenges to come on the international stage.
After a campaign fought almost exclusively along domestic lines, politicians and commentators abroad were assessing the impact of the Conservatives' win.
Thoughts turned in particular to Mr Cameron's promise to hold a referendum on the UK's EU membership, which he reaffirmed yesterday.
A spokesman for European Commission President Jean-Claude Juncker said he was "looking forward to meeting Mr Cameron soon" and congratulated him on his victory.
Mr Juncker will examine in a "very polite, friendly and objective way" any proposals, ideas or requests that the UK puts forward.
However, his office also warned that principles such as freedom of movement were "non-negotiable", the BBC reported.
Manfred Weber, chairman of centre-right group the European People's Party, congratulated Mr Cameron.
He wrote on Twitter: "On the referendum, the ball is in Mr Cameron's court. He has to put his demands on the table. But EU freedoms will not be negotiable.
"We Europeans must also start thinking about whether it is time for a larger Treaty reform."
There was also a reminder of the deterioration in the relationship with Russia, which shows little sign of improvement.
In comments referred to on Twitter by Russian ambassador to Britain Alexander Yakovenko, a spokesman for the Kremlin insisted the relations were "frozen not by our fault", adding that they are " interested in mutually beneficial ties" with all nations, including the UK.
There were, however, plenty of fulsome congratulations for the Prime Minister.
They were led by US president Barack Obama, congratulating Mr Cameron on an "impressive electoral victory".
He said: "The special and essential relationship between the United States and the United Kingdom is rooted in deep and abiding shared interests and values.
"I have enjoyed working closely with Prime Minister Cameron on a range of shared interests these last several years, and I look forward to continuing to strengthen the bonds between our countries, as we work together on behalf of global peace, security and prosperity."
Downing Street said the Prime Minister received a phone calls from French president Francois Hollande, who invited him to Paris for talks on the EU and international issues.
Italian premier Matteo Renzi called to salute an "incredible" result, No 10 said.
Japan's prime minister Shinzo Abe tweeted to Mr Cameron: " Huge congratulations on your splendid victory in the general election."
Indian premier Narendra Modi and Israeli leader Benjamin Netanyahu also offered their congratulations.
Nicolas Sarkozy, the former French president attempting to mount a political comeback, tweeted: "Heartfelt congratulations to you @David_Cameron on your impressive victory."
The election result was leading news bulletins around the world.
It was the lead story on the websites of two of the leading newspapers in the US - the New York Times and the Washington Post.
The New York Times observed that the campaign had "centred primarily on domestic issues" such as austerity and the NHS, adding: "Mr Cameron had also played up fears that a Labour government, reliant on support from the Scottish nationalists, would drive the country leftward and risk the nation being splintered."
As well as announcing Voters Keep Cameron In Power, the Washington Post gave particular prominence to the SNP's stunning success with the headline: " Election results produce seismic shift in Scotland."
Much of the coverage abroad focused on the SNP's sweeping gains north of the border.
French newspaper Le Monde proclaimed nationalist leader Nicola Sturgeon the "star of the campaign" and "the new Iron Lady of Scotland".
A commentator for German news magazine Der Spiegel described the result as "bad news for Europe".
Downing Street said that German Chancellor Angela Merkel had called Mr Cameron to congratulate him on a "simply great" result.
The pair agreed to talk more soon and Mr Cameron said he was looking forward to the summit of the G7 group of major industrialised powers which Germany is hosting in Bavaria next month.
Downing Street later said that Mr Cameron took a call from Mr Obama, who told him he was "a great partner" and the US President was "thrilled to keep working together".