Oil giant Shell on Monday said two new leaks had occurred on one of its pipelines in southern Nigeria after similar incidents in recent days blamed on crude theft.

"Two new leaks were reported today on the Trans Niger pipeline at Akpajo and K-Dere in Ogoniland, after a similar number of leaks caused by hacksaw cuts were repaired at the weekend," Precious Okolobo, spokesman for Shell's Nigerian joint venture, said in a statement.

He did not disclose the extent of the leaks and when repairs would begin, but said later that the affected line "has been isolated and production switched to an alternative line."

"A joint investigation team will determine the cause and extent of the leaks preparatory to repair work," the statement said.

The Anglo-Dutch firm announced on Friday a significant cut in its Nigerian oil production due to pipeline damage caused by theft, and warned that it might not meet contractual obligations as a result.

A shutdown of the damaged line for repairs will cut output by 60,000 barrels per day in Africa's largest crude producer, it said. Nigeria has been producing between 2.0 and 2.4 million barrels per day in recent months.

Oil theft has been a growing problem in Nigeria, and Shell chief executive Peter Voser said last month that there have been estimates that 150,000 barrels of oil and condensate is stolen in the country each day.

The theft often causes damage to pipelines, resulting in production halts.

However, activists argue that Shell has not done enough to prevent spills and clean them when they occur.

The company faced criticism from the United Nations on the issue when the world body issued a landmark report on Nigerian oil pollution last year.