Hours after the Gambia's former President Yahya Jammeh left the country after 22 years in power, West African troops approached the capital to secure the arrival of President Adama Barrow from Senegal.
A Senegalese general leading a joint force of troops from five African countries said on Sunday that the soldiers entered the Gambia to control the strategic points to ensure the safety of the population and facilitate Barrow's assumption of his role.
Witnesses in the Gambian border town of Farafenni saw a convoy crossing the frontier on Sunday morning. It could take them several hours to reach the capital Banjul.
Marcel Alain de Souza, a top official with the Economic Community Of West African States (ECOWAS) said pro-Jammeh mercenaries had opened fired as troops crossed the border. "They were neutralized," he said in a statement.
The official also said Barrow must be in place "as soon as possible."
"A country must have a government, but the security conditions required the troops we have sent to secure Banjul and other towns," De Souza said.
President Barrow has said he would return to the Gambia once a security sweep is complete.
On January 19, the UN Security Council voted on a draft resolution to ensure a transfer of power in the Gambia.
Jammeh flew to Equatorial Guinea following the UN decision with a set of assurances from the international community.
Jammeh left the country after finally conceding defeat in an election under increasing international pressure. He lost the presidential election in December to Barrow but said he would not relinquish power, claiming that there had been irregularities in the vote and pushing the country to the edge of war.
On Saturday, some two days after the expiration of his mandate, Jammeh finally announced a decision "to relinquish the mantle of leadership" and, now with his exit from the Gambia, the way was paved for Barrow to return home from Senegal, where he was inaugurated on January 19.
Jammeh, who took power in a 1994 coup, urged negotiators that he be given amnesty and safe passage out of the Gambia and that his political party be recognized. However, no deal on amnesty was finalized with the negotiators and Jammeh was forced to go into exile.
His family and aides were to depart on a separate plane.
The fate of his party was not immediately clear.
During Jammeh's reign, his government was accused of harsh treatment of opponents.
