Police in the Maldives have stopped a presidential election from going ahead on Saturday, plunging the country into fresh political uncertainty.
Electoral commission head Fuwad Thowfeek said police had entered his offices and were stopping officials distributing election materials.
The Maldives has been in turmoil since ex-President Mohamed Nasheed was ousted in disputed circumstances in 2012.
The latest move has caused alarm among the country's international partners.
India's foreign ministry said it was "seriously concerned at attempts to stall the democratic process".
A US embassy official in Sri Lanka said the failure to hold Saturday's election "represents a real threat to democracy in Maldives".
UK Foreign Secretary William Hague said he was "deeply dismayed" and called for the democratic process in the Maldives to be allowed to proceed.
Commonwealth observers in the country also issued an angry statement denying suggestions by the police that they had sought Commonwealth advice before stopping the election.
In a televised speech, Mr Thowfeek said it was a "dark day for democracy".
Correspondents said the Maldives' capital, Male, appeared calm early on Saturday, with people still waking up to the news.
Mr Nasheed is standing in the election but the two candidates who trailed behind him in an earlier vote - held last month but then annulled - have been fighting for it not to take place.
Late on Friday, Gasim Ibrahim and Abdulla Yameen sought an injunction against the election at the Supreme Court.
They complained that they hadn't had time to endorse the registry of voters - a newly introduced requirement.
The court didn't issue an injunction but nor did it give a clear instruction for the election to go ahead.
Police spokesman Abdulla Nawaz said the election was stopped because the commission did not comply with a court order to have the voters' list endorsed by all candidates.
But Mr Thowfeek accused them of exceeding their mandate.
"We are very much concerned about what is going on in this country. The Supreme Court decision does not ask police officers to look into the voters' list and check what is there," he told reporters.
Last week, the Maldives Supreme Court annulled the result of the first round of the elections held in September because of alleged irregularities.
Mr Nasheed, now the main opposition leader in the Indian Ocean archipelago, won 45% in that poll against 5% for current President Mohamed Waheed.
Mr Waheed has since withdrawn from the election.
Analysts say that if his replacement is not elected by the end of his official term in three weeks, it will spark a constitutional crisis.
Early on Saturday, Mr Thowfeek had announced: "We will hold the election in accordance with the guidelines issued by the Supreme Court.
"The start of the voting may be delayed in some places, but we will allow more time for people to cast their ballots."
However, within hours police were at the electoral commission and Mr Thowfeek was obliged to call the election off.
"Police personnel in this building stopped us taking anything from here [election offices], so we have no other option except to stop the election today," he said.
"A new date for elections will be informed later," he added.
International observers had all praised the conduct of the first-round election, and the Supreme Court's decision to annul it was condemned by Mr Nasheed's supporters.
Mr Nasheed came to power in 2008 in the Maldives' first free elections, but resigned amid violent protests and a mutiny by senior police officers in February 2012.