Resolution passed by national assembly allows president to stay in power for 90 more days despite losing December vote.
Large numbers of Gambians have fled their homes and soldiers from neighbouring Senegal have begun moving towards the borders amid a deepening political crisis.
Yahya Jammeh, who lost a December 1 presidential vote to opposition leader Adama Barrow, is refusing to step down, despite international condemnation and a threat of a military intervention by West African countries to enforce his election defeat.
The president’s mandate expires on Thursday, and Barrow – who is currently in Senegal – has pledged to go ahead with his inauguration on Thursday.
Halifa Sallah, a spokesman for the president-elect, said if Jammeh
refused to step down by midnight, the inauguration would take place at the Gambian embassy in Dakar.
Late on Wednesday, witnesses reported seeing Senegalese soldiers in both the Kaolack region of Senegal to the north of The Gambia, and in the southern Senegalese region of Casamance.
The Gambia is completely surrounded by Senegal and the Atlantic.
Colonel Abdou Ndiaye, a spokesman for the Senegal army, told Reuters news agency that Senegalese troops arrived at the Gambian border late on Wednesday.
“We are ready and are awaiting the deadline at midnight. If no political solution is found, we will step in,” Ndiaye said.
After the midnight deadline, there was no word from Jammeh.
Al Jazeera’s Ahmed Idris, reporting from Nigeria’s capital, Abuja, said that according to multiple security sources, a “deployment comprising of air component, the navy as well as ground troops was under way to go to Gambia.
“A ship of the Nigerian navy is off the coast of Ghana on the way to Gambia, and there are reports that Ghana may also be contributing to the troops’ deployment to Gambia, in addition to Senegal.”
In a Facebook post, Mai Ahmad Fatty, Barrow’s special adviser, advised Gambians to stay indoors.
“Those who resist peaceful change effective 12 midnight tonight shall face definite consequences, to their peril,” he wrote.
“Anyone with firearms tonight shall be deemed a rebel, and will certainly become a legitimate target.”
As the crisis has deepened, hundreds of tourists have departed from The Gambia, a popular winter destination in West Africa for visitors, especially from Britain, the former colonial power.
The streets of the capital, Banjul, were largely empty by late afternoon on Wednesday.
“The town today has been calm, especially downtown has been almost deserted,” Katarina Hoije, a Banjul-based journalist, told Al Jazeera.
“Shopkeepers have kept their stores closed while police and military have been patrolling the neighbourhoods in the city centre.
“In other neighbourhoods of the town, further away from the government buildings, life goes on as usual but of course there is an anticipation of what is going to happen on Thursday.”
At least 26,000 people have fled The Gambia for Senegal since the start of the crisis fearing unrest, the UN’s refugee agency UNHCR said on Wednesday, citing Senegalese government figures.
At the Bundung Garage bus station in Banjul, women carrying infants strapped to their backs queued up to get the belongings they had salvaged onto buses bound for the southern border with Senegal.
Men and children sat patiently amid piles of suitcases, rolled up foam mattresses, bags of rice and bottles of cooking oil.
Others fled on pirogues across the river that splits the country down the middle.
A former coup leader who has ruled the small West African country since 1994, Jammeh initially conceded defeat but a week later contested the poll’s results stating irregularities.
In a sign he is digging in, Gambia’s National Assembly passed a resolution on Wednesday to allow Jammeh to stay in office for three more months from Wednesday.
The decision came a day after Jammeh declared a 90-day state of emergency, alleging “unprecedented and extraordinary amount of foreign interference” in the country’s internal affairs.
But Jammeh’s allies have deserted in their droves – at least eight ministers have so far resigned of whom four quit in the past 48 hours – and it is unclear how many of his own armed forces will be willing to defend him once his mandate expires.
The Gambia is one of Africa’s smallest countries and has had only two rulers since independence in 1965.