Gambian President Yahya Jammeh will be “strongly sanctioned” if he tries to stay in power, the UN’s regional envoy, Mohammed Ibn Chambas, has said.

Mr Ibn Chambas also called on the Gambian army to leave the country’s electoral commission office, which it seized on Tuesday.

The seizure was an “outrageous act of disrespect of the will of the Gambian people”, he said.

Mr Jammeh initially conceded defeat to Adama Barrow before changing his mind.

He has since challenged the election outcome in the Gambian supreme court.

But Mr Ibn Chambas, who visited The Gambia on Tuesday, said the legal process was separate from Mr Jammeh’s mandate as president and he had to step down when it ends on 19 January.

“For Mr Jammeh, the end is here and under no circumstances can he continue to be president,” he said.

It is also unclear how Mr Jammeh’s supreme court challenge can proceed because only one of its seven judges are in post.