Johannesburg - A South African sound engineer kidnapped by gunmen in Nigeria's restive Niger Delta oil region has been released, his employer television company M-Net said on Tuesday.

M-Net said Nick Greyling, who was kidnapped with two colleagues all working for the SuperSport satellite channel on March 1, was released late on Monday.

Talk Radio 702 reported that South African authorities in Nigeria and Nigerian police negotiated the release of Greyling.

Neither South African government officials nor Nigerian police officials were immediately available for comment.

Foreigners, usually working for oil firms, are often kidnapped for ransom in the Niger Delta. Wealthy Nigerians are also frequent targets for the kidnappers.

Thousands of gunmen put down their weapons last year as part of a presidential amnesty aimed at oil militants, but critics say common criminals were among those pardoned and that crime will rise as former rebels seek other sources of income.