LAGOS - Anglo-Dutch oil group Shell said yesterday it has shut in 25000 barrels a day of crude in a southern Nigerian oil field due to spills caused by sabotage and theft.

"The Shell Petroleum Development Company of Nigeria has shut in production from Imo River Field due to a recent upsurge of illegal bunkering and refining activities that have impacted on the environment," the company said.

Theft of crude is commonly referred to as "bunkering" in Nigeria.

Shell said the field, which straddles oil-producing Abia and Rivers states, has five flow stations, a gas compressor station and several kilometres of pipelines among other faculties.

The thefts were first noticed in the field two years ago, prompting government security forces to move in to dislodge the perpetrators and destroy their barges and canoes.

Pipeline vandalism and associated spills are common in the Niger Delta, Nigeria's oil and gas producing region, to feed a lucrative black market.