Abuja: A 20-member crew of an oil tanker, seized by pirates off the coast of Nigeria five days ago, has been set free unharmed by their captors.

The tanker, MT Cape Bird was hijacked by the pirates 90 nautical kilometres off the coast of the oil-rich African country's commercial capital of Lagos.

A spokesperson for Columbia Ship management GmbH of Hamburg said on Friday that they were left to sail to safety by the assailants.

The crew included Russians, Georgians, Ukrainians and Latvians.
Ransoms are normally paid to pirates before they release any ship but the spokesperson of the ship refused to say anything on the issue.

A spokesperson for the Nigerian Navy refused to comment on the ransom issue but disclosed that the ship conveyed 30,000 tonnes of fuel.

In Africa, piracy occurs mostly off Somalia coast but Nigeria's oil militants based in the oil-rich Niger Delta region often carry out hijacking of oil tankers.

In mid-July, a Greek oil tanker has been hijacked off the coast of Nigeria with its 20 crew members by armed men.

The ship 'Aegean Star' belonged to Endeavour Marine Agency based in the Greece's main port of Piraeus.

The oil tanker which was flying a Liberian flag had sailed from West African country of Ghana on its way to Benin and was commandeered by pirates 30 nautical miles off Nigerian coast.

International Maritime Bureau (IMB) announced recently that attack on ships is on the increase. In 2011 alone, 266 piracy attacks have been recorded, a big increase compared to the 196 figure of early last year, it added.