President Muhammadu Buhari has ordered security to be stepped up in Nigeria's oil-producing south, after a spate of attacks blamed on local militants that he said threatened the economy.
Buhari on Friday met senior executives of the Anglo-Dutch oil group Shell, whose Nigerian subsidiary has been targeted in recent months by a group calling itself the Niger Delta Avengers.
The group wants a fairer share of oil revenue for local people and wants a government amnesty programme that brought similar unrest to an end in 2009 to be continued.
A statement from Buhari's office said Nigeria's naval chief had been ordered "to reorganise and strengthen the military joint task force (JTF) in the Niger Delta to deal effectively with the resurgence of militancy and the sabotage of oil installations".
JTF operations "were also being enhanced with increased support and cooperation from the United States and Europe in the areas of training, intelligence, equipment and logistics", it added.
"We have to be very serious with the situation in the Niger Delta because it threatens the national economy," Buhari told Shell's upstream head Andrew Brown.
"I assure you that everything possible will be done to protect personnel and oil assets in the region."
Nigeria has recently lost its status as Africa's leading oil producer to Angola because of the cut in output from sabotage, attacks and leaks.
The government, which relies on oil exports for 70 percent of revenue but has seen income slashed because of a global slump in the cost of crude, has budgeted for 2.2 million barrels per day this year.
But Vice-President Yemi Osinbajo has said output is now at just 1.4 million bpd.
Shell reportedly evacuated personnel from an offshore installation recently after militants targeted US group Chevron while on Wednesday rebels bombed a gas pipeline owned by a subsidiary of Italy's Eni.
The Niger Delta Avengers in February claimed an attack on an undersea pipeline that forced Shell to shut its Forcados terminal.
Early on Friday, suspected militants blew up another gas pipeline operated by the state-run Nigerian National Petroleum Corporation (NNPC) in Delta State, according to locals.