An unidentified number of Bulgarian and Belgian policemen have been blocked at a hotel in Niger's capital, Niamey, following a coup and the capture of the president, reports say.

The policemen made a transitional landing in Niger on their way to repatriate foreign applicants for refuge, who have been turned down by the Belgian authorities, the Bulgarian National Radio reported. 

The operation is being carried out by the Belgian services and with the cooperation of their Bulgarian colleagues.

A coup took place in Niger on Thursday and the president has been captured after a gun battle in the capital, Niamey.

In a television announcement, a spokesman for the plotters said Niger's constitution had been suspended and all state institutions dissolved.

The country was now being led by a group called the Supreme Council for the Restoration of Democracy (CSRD), the spokesman said.

President Mamadou Tandja is believed to be in captivity at a military barracks.

Reports say government ministers are also being held.

Making the announcement on television, the spokesman for the coup leaders, wearing a military uniform, was surrounded by a large group of soldiers.

He called on the people of Niger to "remain calm and stay united around the ideals postulated by the CSRD", to "make Niger an example of democracy and good governance".

"We call on national and international opinions to support us in our patriotic action to save Niger and its population from poverty, deception and corruption," he added.

A newsreader on Niger television said the country's borders had been closed and a curfew was now in force.

Tensions have been growing since last year in the uranium-rich nation.

Tandja has been widely criticised when he changed the constitution in August to allow him to stand for a third term.