The worldwide relations minister, Netumbo Nandi-Ndaitwah, said Namibia supports the Economic Community of West African States (Ecowas), which have called on Jammeh to leave. "Barrow's assumption of his role".
Several witnesses in Barra, a town on the opposite bank of the Gambia River from Banjul, saw scores of soldiers massing near a ferry terminal.
Forces from Senegal, which completely surrounds the former British colony's land borders, had entered briefly on Thursday but pulled out shortly afterwards.
A member of Barrow's coalition rejected claims they had signed a declaration of for Jammeh that was supported by the Economic Community of West African States (ECOWAS).
Amnesty International issued a statement that said Gambia would become a model of democracy and that its citizens can now stop living in fear.
The official also said Barrow must be in place "as soon as possible".
Jammeh initially refused to step down.
"No legislative measures" would be taken that would infringe the "dignity, security, safety and rights" of Jammeh or his family, it said, noting that he could return when he pleased and that property "lawfully" belonging to him would not be seized.
Recently inaugurated president of The Gambia, Adama Barrow, has revealed he will be ruling the country from his hide out in Dakar, Senegal until he gets security clearance from ECOWAS. "Gambia will neither respect nor honour what was contained in that joint declaration".
Experts told AFP the document was not legally binding and would be left to the interpretation of the new government.
Rights groups accuse Jammeh of jailing, torturing and killing his political opponents while acquiring a vast fortune - including luxury cars and an estate in the United States - as most of his people remained impoverished.
"As a result of all the numerous sacrifices that we have made as a nation, the Gambia has affirmed its desire to determine its own future and destiny".
The former president left Banjul on Saturday to go into exile after he was pressurised by the ECOWAS to rescind his earlier decision not to accept the outcome of December 1 presidential election, which saw him losing to the opposition candidate, Adama Bbarrow. "Everyone is free. You can do whatever you want, because this is a democratic country".
According to the U.N. refugee agency UNHCR (United Nations High Commissioner for Refugees), about 45,000 Gambians, mainly children, had fled to Senegal since January 1.