Nairobi/Abuja, Jan 30 (DPA) Nigeria's main militant group Saturday called off a three-month ceasefire and warned that oil companies in the Niger Delta should expect an 'all-out onslaught' against facilities and personnel.

Attacks by the Movement for the Emancipation of the Niger Delta (MEND) had slashed the West African nation's oil production by around a quarter and helped drive up global oil prices when MEND responded to a government amnesty and laid down its arms last October.

However, MEND spokesman Jomo Gbomo said in an emailed statement that his group had become disillusioned by the government's failure to create real dialogue.

'It is sufficiently clear at this point in time that the government of Nigeria has no intentions of considering the demands made by this group for the control of the resources and land of the Niger Delta to be reverted to the rightful owners, the people of the Niger Delta,' he said.

MEND says it is fighting for a share of oil revenue for Niger Delta residents, who complain that multinational oil companies have ruined their agriculture and fishing livelihoods and caused major environmental damage in the delta's creeks.

Gbomo said that the group would now redouble its efforts to sabotage the oil industry.

'All companies related to the oil industry in the Niger Delta should prepare for an all-out onslaught against their installations and personnel. Nothing will be spared,' he said.

The announcement will come as a blow to Nigeria, which was slowly beginning to ramp up its oil production again.

Attacks by MEND and the syphoning off of oil by criminal gangs slashed the West African nation's oil production from 2.6 million barrels per day in early 2006 to around 1.7 million barrels prior to the amnesty.