Five men were accused of terrorism: of training with an al-Qaida-linked Algerian militant group and plotting to blow up government buildings in Africa's most-populous nation.
Prosecutors said the men, whose arrest was announced earlier this month, had trained for more than a year until August with Algeria's Salafist Group for Call and Combat, which changed its name to al-Qaida in Islamic North Africa in January after it formally linked with al-Qaida.
All were charged with terrorism in a court in the capital, Abuja. The suspects, who didn't enter a plea on Thursday, had firearms, dynamite and other explosives and had planned to target government buildings, prosecutors said.
Officials couldn't immediately be reached to give a maximum punishment for the suspects, if convicted. Court was adjourned until Nov. 29.
The charge sheet did not mention a planned attack on any diplomatic or other international installations in Nigeria. The U.S. representation in the main city of Lagos said before the Sept. 11 anniversary this year that it had information that militants could be planning to attack the embassy or other U.S. government buildings.
In one audio recording, Osama Bin Laden warned leaders of Nigeria and other nations not to help the U.S. Nigeria, a supplier of oil to the United States, has 140 million people split about evenly between Christians and Muslims.
But no evidence has ever been made public that directly places members of bin Laden's organization in Nigeria.
Militants linked to the North African militant group have been arrested in several countries across the strip of desert just below the Sahara Desert known as the Sahel, which includes northern Nigeria.
The choice of the city of Helsinki is not incidental as the capital of Finland had hosted US-Soviet negotiations on the limitation of nuclear stockpiles in 1969