The UN has backed efforts to remove Yahya Jammeh from power
Senegalese troops have invaded Gambia to get the country's former leader to cede power to newly-inaugurated president Adama Barrow.
Former president Yahya Jammeh has refused to step down from office, saying he does not accept the result of an election held in December.
The United Nations Security Council has backed the efforts of the west African bloc of nations, ECOWAS, to remove Jammeh from power by force.
It comes just hours after Mr Barrow was sworn in as president at Gambia's embassy in neigbouring Senegal.
Mr Barrow said his inauguration was "a victory of the Gambian nation".
He said: "Our national flag will fly high among those of the most democratic nations of the world."
Mr Barrow (51) also warned armed forces to "remain in their barracks" and said anyone "found wanting or in possession of firearms without my order will be considered rebels".
According to news agency AFP, Gambian army chief Ousman Badjie said he would not engage his soldiers in a "political dispute".
Reporting from Gambian capital Banjul, reporter Stuart Ramsay said thousands of people had flocked to the streets in "remarkable scenes".
He said: "People are beeping their horns, there are a lot of people waving to people trying to drive by.
"We have seen some soldiers being deployed in certain areas but they don't seem to be intervening in any particular way."
He added: "There doesn't seem to be any violence per se but lots of people are shouting and celebrating what they see as a change of power."
The political crisis prompted the evacuation of thousands of tousists from Gambia as the threat of a military action grew.
The Department of Foreign Affairs is advising citizens to avoid non-essential travel to the West African nation.
Until a matter of months ago Mr Barrow was a political unknown, but was thrust into the limelight when eight opposition parties put him forward as a unifying figure.
The 51-year-old lived in Britain for three-and-a-half years when he was younger, and worked at an Argos store in London.