WARSHIPS from the Nigerian navy surrounded four oil rigs on which 97 foreign oil workers were being held hostage yesterday, as part of a “peaceful” operation to end an 11-day confrontation in the Gulf of Guinea, south of the Niger Delta.

Negotiations between the rig owner, Transocean, and Nigerian unions ended in deadlock yesterday, leaving the hostages, including 35 Britons, stranded on the deep water rigs amid mounting concerns for their safety.

The navy said it would not try to storm the platforms, and would instead try to reach a peaceful resolution.

The rigs have been seized by an estimated 100 Nigerian oil workers in a protest over the dismissal of five workers. Strikers have blocked access to the helicopter landing pads and docking bays on board the rigs in the Gulf of Guinea, 25 miles off the coast of Nigeria’s Niger Delta region, which are operated by Houston-based Transocean, the world’s largest off-shore drilling contractor.

Shell confirmed yesterday that it had leased three of the rigs and that eight Shell staff, including three Britons, were among the hostages.

Some of the hostages have expressed fears that their captors might kill them or blow up the rigs if the Nigerian authorities, who have a reputation for taking an uncompromising stance over oil industry disputes, try to bring about their release by force.

“Make no mistake of the danger we’re in,” one British hostage said in an e-mail message to his union representative. “If they have lost everything, then they will make sure we lose everything. And that means our lives,” he added.

But Transocean officials have dismissed reports that the expatriates have been threatened. “The situation on all four rigs is calm,” a company spokesman said. “No one has been hurt. We are trying to resolve the situation as quickly as possible.”

The strike began peacefully but turned nasty after the company fired five of its Nigerian workers for alleged theft.

A diary kept by one of the hostages, and sent by e-mail to worried relatives, describes how two expatriates were taken off one of the rigs after suffering “nervous breakdowns”.

Another entry describes the anger of the strikers after rumours that the Nigerian navy might be called in. “Some crew members started running around the rig with a fire axe.”