Nigerian authorities have charged five suspected Islamic militants with a plot to attack government buildings.
Nigeria is wary that it could become a terror target
Three of the men spent two years in an Algerian training camp run by a group with al-Qaeda links, prosecutors said.
The men were arrested in northern Nigeria earlier this month by members of the country's security services. They have not yet entered a plea.
Nigeria has arrested several suspected Islamic militants in the past, but no convictions have ever been brought.
Nor has there ever been any substantive evidence produced of any terrorist operation planned in Nigeria, says the BBC's Alex Last in the country.
Three of the accused men had undergone training in Algeria between 2005 and August 2007, with a group known at the time as the Salafist Group for Preaching and Combat (GSPC), prosecutors said.
The GSPC renamed itself al-Qaeda in the Islamic Maghreb in January 2007, after reportedly receiving authorisation from Osama Bin Laden to brand itself as an al-Qaeda affiliate.
No international targets
The men were in possession of a rifle, live ammunition, seven sticks of dynamite, a bag of fertiliser and other explosives when they were arrested, authorities said.
The arrests followed reports received by officials at the US embassy in Nigeria that Islamic militants were planning to attack US government buildings in the country.
The BBC's Alex Last says that Britain and the US have long been concerned that al-Qaeda-style groups could be set up in Nigeria.
The accused men have not been charged with preparing an attack against international targets in the country, however.