Militants in Nigeria's southern Niger Delta warned on Friday they would carry out more kidnappings from oil installations after the military rescued 19 hostages from one of their camps this week.

The hostages - two Americans, two Frenchmen, two Indonesians, one Canadian and 12 Nigerians - were rescued late on Wednesday in what the government has heralded as a major victory for the military in the restive region.

"Our fighters have being instructed to carry out more raids on oil installations from where fresh hostages will be taken," the Movement for the Emancipation of the Niger Delta (MEND) said in a statement emailed to media.

The group also said it had clashed with the army on Thursday in Delta, one of the three main oil-producing states in the region, and that several soldiers had been killed. There was no independent confirmation of any casualties.

The military taskforce in the region said it was engaged in an "ongoing operation" against suspected militant camps in the Niger Delta, a vast wetlands region home to Africa's biggest oil and gas industry.

Sources in Delta state said the army raided a camp belonging to a militant leader called John Togo in the creeks on the border between Delta and neighbouring Bayelsa state on Thursday.

"There is a need (for the military) to take over all these camps. This operation will continue as long as it will take to uproot the militants from the Niger Delta," Major General Charles Omoregie, commander of the military taskforce, said.

source: Reuters