President Yahya Jammeh is frequently criticised by rights groups.

In recent years, he has publicly threatened to kill gay people and rights workers.

Last month the government of Jammeh, who took power in a bloodless coup in 1994, expelled the envoy of the UN's children charity, Unicef.

Saho, who served in Jammeh's government from 1994 until he was sacked last month, was taken from his home on Friday night.

Police said he was wanted for questioning by intelligence officials.

His family has not been able to contact him since and no official reason has been given for his arrest.

"According to our constitution, within three hours of an arrest the person should be told why he or she has been arrested," Sallah told the BBC's Network Africa programme.

He said relatives of people arrested as far back as October had told him they had not been able to contact their detained family members.

He said those arrested in the more recent wave of arrests were in the same situation.

"We've still been unable to establish why they've been arrested, and as it stands there is only speculation," he added.

Sallah, of the National Alliance for Democracy, has himself been arrested several times in recent years. (BBC)