The declaration was necessary “due to the unprecedented and extraordinary amount of foreign inference in the December 1 presidential elections and also in the internal affairs of The Gambia,” Jammeh said on state television.
This had created an “unwarranted hostile atmosphere, threatening the sovereignty, peace, security and stability of the country,” he added.
The move comes just two days ahead of Thursday’s planned inauguration of his rival, Barrow, whose election victory Jammeh initially recognised before promptly changing his mind.
Opposition leaders say the state of emergency could allow the government to cancel or postpone Barrow’s inauguration.
According to the Gambian constitution a state of emergency lasts seven days if the president declares it unilaterally, but up to 90 days if the national assembly confirms it.