The UN Security Council has condemned Gambia President Yahya Jammeh's rejection of election results announced last week that knocked him from power after 22 years, and it urged all parties to refrain from violence.
Gambia's President-elect Adama Barrow said Mr Jammeh had no authority to reject the results of the 1 December polls, while the UN and African Union pressured Mr Jammeh to step aside.
"[Security Council members] called on him to respect the choice of the sovereign People of The Gambia, as he did on 2 December 2016, and to transfer, without condition and undue delay, power to the President-elect, Mr Adama Barrow," it said in a statement.
Mr Jammeh on Friday called for another election in the tiny West African country after narrowly losing to opposition leader Mr Barrow, jeopardising what was expected to be Gambia's first democratic transition of power in over 50 years. He had conceded defeat publicly last week.
The announcement on state television threw the future of the country of 1.8 million into doubt after the unexpected election result ended Mr Jammeh's authoritarian 22-year rule. It had been widely seen as a moment of democratic hope and a chance to end repression in a country known as a police state.
"The outgoing president has no constitutional authority to reject the result of the election and order for fresh elections to be held," Mr Barrow told reporters in Banjul following an emergency meeting under high security.
"I open up a channel of communication to convince him to facilitate a smooth transfer of executive powers in the supreme interest of this country," he said.
The streets of Banjul were calm on Saturday, although some residents said they were staying at home for fear of violence. A strong police presence remained on the streets.
Under Chapter 5 of Gambia's constitution, candidates have 10 days from the declaration of the results to appeal to the Supreme Court.
It was not immediately clear if Mr Jammeh had done that.
As Gambians brace for a tense standoff, international criticism of Mr Jammeh came in fast. Following the US and Senegal, the African Union on Saturday weighed in, calling Mr Jammeh's statement "null and void".
The UN and regional body ECOWAS called on the armed forces to stay neutral. Diplomats have voiced private concerns that a faction of security forces from Mr Jammeh's Jola ethnic minority might protect Mr Jammeh, potentially provoking broader conflict along ethnic lines.
Senegal, which has Gambia's only land border, has called for an emergency meeting of the Security Council and "solemnly" warned Mr Jammeh not to harm Senegal's interests or its citizens in Gambia.
ECOWAS, the African Union and the UN called jointly for all parties to "reject violence and peacefully uphold the will of the people".
But in a sign that early mediation efforts are floundering, Senegal's foreign minister said that Gambian authorities had refused entry to the chair of regional body ECOWAS.
"Johnson Sirleaf was supposed to fly in today, but Mr Jammeh said 'not at the moment,'" Senegalese Foreign Minister Mankeur Ndiaye told Reuters. It was not clear if the plane had already taken off.
It was unclear what the Security Council was planning, but military intervention was one option, diplomats said, without giving details. There is precedent for this: for example, Senegal's army intervened in Gambia in 1981 during a coup.
A third party candidate in last week's election, Mama Kandeh of the Gambia Democratic Congress also rejected Mr Jammeh's call for another election.
"Your swift decision earlier to concede defeat and your subsequent move to call Adama Barrow to congratulate him was lauded throughout the world," Mr Kandeh said. "We therefore prevail on you to reconsider your decision."