DAKAR, Senegal (AP) — The African Union is calling the sudden rejection by Gambia's longtime leader of his election defeat "null and void" as the tiny West African nation is urged to remain calm.

President Yahya Jammeh late Friday announced that he no longer accepts defeat in the presidential election, a week after he jovially conceded to his rival Adama Barrow.

Jammeh said investigations since the Dec. 1 vote revealed a number of voting irregularities.

The AU statement stresses the urgent need for a peaceful transfer of power and calls on security forces to remain neutral.

Mai Ahmad Fatty of the opposition Gambia Moral Congress, one of eight parties that backed Barrow, says the coalition has the will of the people on its side.

Jammeh's 22-year rule has been accused of human rights abuses.