Two explosions have been reported at oil industry facilities in the south of Nigeria just hours after a group claimed it had planted three car bombs.
A suspected bomb exploded at a Shell residential compound in Port Harcourt and another went off near the perimeter fence of a compound of the Italian oil company Agip.
The Movement for the Emancipation of the Niger Delta said it planned to attack strategic locations throughout the oil-rich region.
"What we are fighting for is resource control and we will not stop until we achieve our objective," the group said in a statement to the Associated Press new agency.
Residents reported hearing explosions and seeing a large plume of smoke rising over the city.
Workers abducted
Bassie Inyang, a police official in the city, said police and bomb disposal experts at both locations had no reports of casualties.
Both blasts appeared to hit residential compounds when most workers would be in their offices.
Much of the Niger Delta oil-pumping infrastructure is sited away from highly-populated areas like Port Harcourt, making it unlikely Monday's blast would result in large reductions in oil production.
The group is currently holding four foreign oil workers, three Italians and one Lebanese, who were taken hostage on December 7.
It also detonated two car bombs earlier this year, one at a military barracks in Port Harcourt and another near an oil refinery in Warri.
Attacks on pipelines and oil facilities have cut the West African country's usual daily output of 2.5 million barrels by about a quarter this year.