Gunmen in Nigeria have kidnapped two Lebanese construction workers in the southern oil-producing Niger Delta and are demanding a ransom for their release, security sources told Reuters.

The men were working for Setraco, a local engineering company specialising in building roads and bridges, when they were kidnapped near the town of Amassoma yesterday , one of the sources -- a private security contractor -- said.

"Ransom has been demanded by an unknown group," he said.

Militants who say they are fighting for greater local control of oil resources in the Niger Delta, home to Africa's biggest oil industry, have carried out numerous attacks since 2006, blowing up pipelines and sabotaging industry facilities.

The unrest has helped push world oil prices to record highs.

The Nigerian authorities have made some progress combating oil theft, known locally as "bunkering", but this has led criminal gangs to seek other forms of income and there have been numerous kidnappings for ransom.

A Maltese oil worker , George Scerri of Birkirkara, and a Pakistani, employed by oil services company Lonestar were kidnapped in the Niger Delta almost two weeks ago.

More than 200 foreigners have been seized in violence in the region since early 2006. Almost all have been released unharmed.