Nigeria wants Royal Dutch Shell Plc (NYSE: RDS.A) to reopen a major export pipeline in the Niger Delta but the oil major wants better protection first to avoid having it blown up yet again, officials and industry sources said.

Militants fighting for a share of oil revenues have attacked the Trans Forcados Pipeline, the primary line feeding oil to the 400,000 barrel per day Forcados export terminal, several times in the past 12 months.

A more sophisticated strike in 2016 used divers to blow up a hard-to-fix section some six meters underwater, forcing Shell to fly in expensive specialist underwater engineers and spend some six months on repairs.

Militants attacked again shortly after it reopened, meaning Shell has spent all but about three weeks of the past year repairing the shut-down pipeline.

The Delta state government, whose revenues are linked to volumes of oil in the pipeline passing through its territory, has been asking Shell when it will resume pumping, promising extra security.

"We are concerned [about the closure]," said Charles Ehiedu Aniagwu, spokesman for the Delta government. "We are talking to them [Shell] and people for a lasting peace."

Local officials have set up a committee to improve security by talking to oil firms and communities where militants often hide in the southern swampland.

But he said the federal government needed to help because the army and police protecting pipelines and other oil facilities report to Abuja.

"We also expect the federal government to do its part in ensuring a smooth working of [International Oil Companies] IOCs," he said.

Vice President Yemi Osinbajo, standing in for President Muhammadu Buhari who is on extended sick leave in London, has been meeting community leaders who act as proxies for militant groups.

He has been promising more development to appease widespread anger among residents over poverty in the Niger Delta, which provides most of Nigeria's oil.

Shell declined to comment.

An industry source said repair works at the Forcados Pipeline had been progressing well, but the main issue was what additional security measures Nigeria could provide to prevent a new attack.

Like other producers, Shell has been monitoring pipelines by helicopter, passing on information to authorities, industry sources said. But the military, which is often accused of graft, has not always been quick to respond.

Experts said the militants must have had insider knowledge to blow up pipelines at spots that are difficult to repair.

Cogent Ojobor, a local leader of the Nigeria Union of Petroleum and Natural Gas Workers (NUPENG), said there would be no pipeline security until the government brokered an agreement to pacify the region.

"Caution is the instrument needed in times of security concerns," he said.