Nigeria soldiers recalled to base

Nigeria has often been ruled by the military

Nigeria's armed forces has cancelled holidays and restricted its soldiers to the barracks while it investigates an alleged breach of national security.

A BBC correspondent says all military officers have been directed to report to their bases.

Several serving and retired soldiers have been questioned following reports of "serious breaches of security".

The former chief security to late dictator Sani Abacha, Hamza al-Mustapha has been linked to the alleged threat.

Mr Mustapha, was seized from prison by police and handed to military intelligence.

'Imminent danger'

But a court has ordered the security forces holding Mr Mustapha to surrender him to a civilian court to face trial for murder.

During Abacha's rule, Mr Mustapha was considered Nigeria's second most powerful official.

In 1998, he was charged with ordering the murder of Kudirat Abiola, the wife of opposition politician Chief Moshood Abiola.

The BBC's Sola Odunfa in Lagos says defence officials have hinted that they may need to interrogate the soldiers in connection with the security breach that has yet to be disclosed.

"There is some level of preparedness, you can say being on alert. It is not any imminent danger that anyone should be anxious about," army spokesman Col Chukwuemeka Onwuamaegbu told the Associated Press news agency.

Nigeria has frequently been ruled by the military, but returned to civilian rule in 1999 with the election of President Olusegun Obasanjo.