Gambia's President-elect has hailed a "new era" for his country.

"My dearest Gambians – the presidency of Yahya Jammeh is officially over," Adama Barrow wrote on Twitter. "The new era of Gambia is here at last."

His message was posted shortly after midnight, when Senegalese forces had threatened to enter the country if outgoing President Jammeh had refused to step down.

Colonel Abdou Ndiaye, a spokesman for the Senegalese army, had said forces were ready to “step in” if no solution to the political unrest in the country was found.

Political tensions have been escalating in Gambia since December, when President Jammeh lost the leadership election to Adama Barrow but refused to leave office, citing irregularities in the vote.

His official mandate ended at midnight and President-elect Barrow had vowed to take office regardless of Mr Jammeh’s position.

“We are ready and are awaiting the deadline at midnight. If no political solution is found, we will step in,” Col Ndiaye said.

The affirmation raises concerns over a potential military confrontation between the neighbouring countries.

President Jammeh had declared a 90-day state of emergency on state TV earlier this week. In the announcement, he also blamed an "unprecedented level of foreign involvement" in Gambia's election.

At least 26,000 people have fled Gambia to Senegal fearing unrest, according to the UN High Commissioner for Refugees (UNHCR), who cited Senegalese government figures.

Thousands of British holidaymakers in The Gambia are waiting to find out when and how they will be flown home, after the Foreign Office updated its travel advice to warn against all but essential travel to the West African nation.

Tour operator Thomas Cook scheduled extra flights to fly home nearly 1,000 holidaymakers on Wednesday. It was also trying to contact a further 2,500 'flight only' tourists in Gambia to arrange for their departure on the earliest available flight, it said in a statement.