Police said those arrested had been taken to a station for questioning

Other worshippers were barred from entering the Juma mosque in Baku, which has been the target of a number of police raids in the past week.

One report said police pulled back when the US ambassador arrived.

Earlier this year, the authorities ordered the 1,000 year-old mosque to close. Its imam, Ilgar Ibrahimoglu is a leading human rights activist.

The authorities say the Juma mosque community is occupying the building illegally, having failed to register with state religious bodies.

But the mosque's leaders believe they are being targeted because Mr Ibrahimoglu is a government critic who was until recently the country's most prominent political prisoner.

[Those arrested] came here not to attend prayers but for other purposes Police officer

Speaking after Monday's arrests, Mr Ibrahimoglu told Turan news agency:

"There is no freedom of conscience and belief in Azerbaijan today."

'Concern'

A police officer told AFP news agency that those arrested "came here not to attend prayers but for other purposes".

The agency said police moved back when US ambassador Reno Harnish went to the mosque to sit in on the prayer ritual.

Last week the US embassy in Baku said in a statement that it was following events at the mosque "with concern".

Last Wednesday police stormed the mosque and expelled worshippers. A new imam backed by the authorities was appointed.

A spokesman for the Azeri justice ministry, Hussein Alikhanov, said worshippers at the mosque were warned repeatedly to vacate the premises.

The closure order followed the trial of Mr Ibrahimoglu, who was jailed for taking part in protests after a disputed presidential election last year that saw a landslide victory for the previous leader's son.

But under pressure from the international community, Mr Ibrahimoglu received a suspended sentence.