Three foreign sailors that were kidnapped last week by pirates in the oil-rich southern region of Nigeria have been rescued, according to the Nigerian Navy.

The three – two Russians and an Indian – were rescued in an operation late on Tuesday by a navy team in the southwestern coastal state of Ondo, spokesperson Suleman Dahun told AFP.

"The rescue happened yesterday around 11 pm," he said, adding that one of the hijackers had been arrested.

Last Thursday, Pirates raided an oil dredger, MV Ambika, in the volatile waters of the Niger Delta.

The pirates killed four naval personnel and kidnapped three foreigners.

The waters off Nigeria have been dogged by cases of kidnappings and killings of naval crews.

Much of the problem is rooted in the Niger Delta, where local residents say they do not feel the benefits of the vast oil wealth of Africa's largest economy.

The country has increased naval patrols but abductions are still common.

Separately, security sources said several pirates had been killed and operations were underway to seize others.