By the BBC's Mark Doyle

The human rights organisation Amnesty International has called for the immediate release from detention of its representative in Gambia who, it said, appeared to have been arrested because of remarks he made on the BBC.

Mr Mohammed Lamine Sillah, who was detained on 22 October, was one of at least a dozen, and probably many more, people - including opposition activists and journalists - who were picked up in the wake of a presidential election held on 18 October.

President Jammeh: First came to power in a military coup

The poll was won by President Yayah Jammeh, who first came to power in a military coup in 1994.

The presidential elections were judged by election observers like the Commonwealth to have been fair on the day of the voting.

But the wave of arrests after the poll may indicate that President Jammeh's government, which first came to power in a military coup, is reverting to its old repressive ways now that the foreign observers have left the country.

The Amnesty International representative in Gambia was detained after telling the BBC about the earlier arrests of opposition activists.

Political detentions

The main opposition party claims that some 60 of its people have been picked up without charge in what appears to have been an exercise in settling political scores.

Although this figure cannot be confirmed, a large number of arrests have taken place. In some cases, members of the youth wing of President Jammeh's ruling party have been moving from house to house pointing out opposition members who are then detained by the police.

At one ruling party rally I saw at least two large anti-aircraft guns

Gambia's former military coup leader won the elections, standing as a civilian, partly by appealing to the youth.

He also exploited the incumbency which his 1994 coup gave him by mobilising the resources of the state behind his ruling political party.

This was particularly noticeable during the campaigning when Mr Jammeh told villagers that if they voted for him they would be rewarded by development projects - but if they voted for the opposition they would get nothing.

Military backing

It was also clear during the campaign that the army supported Mr Jammeh. He was followed during the hustings by a heavy security presence which appeared to exceed the immediate security threat and was interpreted by the opposition as intimidating.

For example, at one ruling party rally I saw at least two large anti-aircraft guns. There is no known armed opposition in Gambia, and certainly none that has aircraft.

At another rally I saw army officers' wives, dressed for the occasion in the uniforms of their husbands. The message was obvious - the army is behind the president.

But Mr Jammeh also won the election by successfully exploiting a split in the opposition, which failed to mobilise behind a single candidate.

That same opposition is now crying foul and pointing to the wave of arrests as proof of the repressive nature of the regime.