Militants who led a deadly attack on a military convoy escorting oil workers in the restive south also abducted 25 Nigerian petroleum-industry employees, the leading oil firm in Africa's biggest producer said on Tuesday.
The hostage takers hadn't made any ransom demands on Tuesday after the attack and seizure a day earlier of the subcontractors working for the Royal Dutch Shell PLC-led joint venture, said a company spokesman, Bisi Ojediran.
Army spokesman Maj Sagir Musa said earlier at least five people died and nine more were missing after around 70 militants in black shirts and red bandanas sank two military patrol boats yesterday in Nigeria's oil-rich southern delta.
Troops were escorting diesel, supplies and employees in the volatile delta region, where attacks over the past year pared away nearly a quarter of Nigeria's usual output.
Nigeria is Africa's largest petroleum producer and the fifth-largest supplier of crude oil to the United States.
Ojediran said no oil workers had been killed or injured in yesterday's attack, although one civilian working for the military had perished.
A group calling itself a coalition of militant groups in the Niger Delta region claimed responsibility.
The coalition demanded the release of imprisoned militant leader Mujahid Dokubo-Asari and said the killings were in revenge for attacks by soldiers on local communities.
However, an e-mail from the Movement for the Emancipation of the Niger Delta, one of the groups the coalition claims to represent, denied responsibility for the attack.
Militant attacks and kidnappings have cut oil production in Africa's largest crude producer by over a quarter so far this year.