LAGOS, Nigeria (Reuters)  Militants in Nigeria’s oil heartland said Saturday they had used missiles, grenades and speedboats in a deadly offensive against army positions, but the military denied it had come under attack.

The militants’ group, called the Movement for the Emancipation of the Niger Delta, known as MEND, said it killed 29 soldiers in attacks in three locations, which it said it were in response to the killing of civilians by security forces.

“Operation Hunter Hunted involved the use of several fast-attack speedboats, general purpose machine guns, rocket-propelled grenades and deadly Soviet-made antitank missiles at close range combat,” MEND said in an e-mail statement. The group said six of its own fighters died in the coordinated attacks.

Lt. Col. Rabe Abubakar, military spokesman for Bayelsa and Delta States, denied the army was under attack, saying soldiers were carrying out regular duties.