In a landmark move to defend democracy, West African troops Thursday entered the tiny West African nation of Gambia, to oust a president who has refused to cede power after an election defeat.
Senegalese troops entered Gambia hours after the incoming president, Adama Barrow, was sworn into office in neighboring Senegal. His predecessor, Yahya Jammeh, has refused to step down despite intense diplomatic pressure and threats of military intervention by other West African nations.
Jammeh last month rejected election results that saw him voted out of office after 22 years in power.
West African forces crossed into Gambian territory after the U.N. Security Council supported Barrow and called on Jammeh to accept defeat.
Barrow, clad in white, was sworn into office at the Gambian embassy, technically Gambian territory, in the Senegalese capital of Dakar. Plans for the inauguration to be held at a major soccer stadium in Banjul, the Gambian capital, were abandoned after Jammeh clung to power.
The swearing-in ceremony — and the military action in support of Barrow — was a hugely significant moment for democracy in Africa, sending reverberations across the continent, as a regional leadership group, Economic Community of West African States, or ECOWAS, stood firm to protect an election, by force if need be.
Shortly before his inauguration, Barrow sent out a tweet: "It is time."
After taking the oath of office, Barrow called on the U.N., African Union and ECOWAS to enforce the outcome of the election.
"As of today, I am the president of Gambians, regardless of whether you voted for me or not," Barrow said, pledging that from now on, life in Gambia would not be about who you know, but what you know.
"This is a victory of the Gambian nation. Our flag will now fly high among the most democratic nations of the world," he said.
There was no comment from Jammeh on Thursday. At one point during the day, Gambia's presidential website appeared to have been hacked, bearing a photograph of Barrow.
Jammeh was left isolated after his term expired at midnight Wednesday and a last-ditch overnight diplomatic effort failed to budge him. Mauritanian President Mohamed Ould Abdel Aziz flew to Banjul on Wednesday in a bid to mediate the crisis, but failed.
Jammeh was reportedly holed up in Gambia's state house, the presidential residence, after he declared a state of emergency on Tuesday, enabling him to rule by decree. Parliament extended his term for 90 days on Wednesday, but Jammeh has been deserted by a raft of government ministers and officials, including Deputy President Isatou Njie-Saidy, who had been in power since 1997.
West African leaders refused to accept Jammeh's efforts to cling to power. In a region where democracy has taken root more deeply than elsewhere in Africa, several presidents are now in office thanks to peaceful elections.
Gambia, a narrow country of 1.9 million people about three-quarters the size of Connecticut, is a former British colony situated on the Gambia River delta.
The West African intervention force involved troops from Senegal and Ghana as well as Nigerian air force special forces.
Nigerian warplanes were reported to be flying over Gambia, ramping up the pressure on the former president.
"ECOWAS has decided, as a result of the refusal of President Yahya Jammeh to accept the verdict of the Gambian people in the elections of December 1, 2016, to deploy troops from its member states to The Gambia with immediate effect," Eugene Arhin, a Ghanaian presidential spokesman, said in a statement Thursday. "The objective is to create an enabling environment of the rule of law and in accordance with the Constitution of The Gambia, facilitate the inauguration of the President-Elect, Adama Barrow, on Thursday, January 19, 2017."
Nigerian Air Marshal Sadique Baba Abubakar addressed Nigerian forces, telling them the mission was clear and urging them to maintain discipline and professionalism.
Jammeh took power in a 1994 coup and has been criticized by rights groups for jailing critics and opponents. He initially accepted his defeat in December's elections but swiftly backtracked, claiming election irregularities and mounting a legal challenge, yet to be heard.
ECOWAS leaders have offered Jammeh immunity from prosecution and exile in Nigeria or Morocco, offers he has rejected.
The crisis is being closely watched across Africa, where many leaders have overturned constitutional term limits to stay on in power, some of them for decades.
The government of Botswana declared Thursday it no longer recognized Jammeh as president. Many international ambassadors were present at Barrow's inauguration.
"Mr. Jammeh's decision not to respect the will of the Gambian people undermines the ongoing efforts to consolidate democracy and good governance in The Gambia and Africa as a whole," Botswana said in a statement.
The statement called on the international community to do everything in its power to exert pressure on Jammeh to leave office.
Thousands of Gambians fled the country Wednesday, fearing unrest, and European tour companies, including some from Britain, evacuated tourists.
Amnesty International researcher Sabrina Mahtani tweeted that the military arrested four young men for selling T-shirts bearing the slogan #GambiaHasDecided — associated with opponents of Jammeh's bid to stay in power. She said they were being held incommunicado.
1 p.m.: This article was updated with actions by the governments of Botswana and Mauritania.