Somali pirates have released an Omani ship they had held hostage for months, a senior government official said on Thursday.

"The Omani ship held for six months was released last night," Abdiqadir Muse Yusuf, assistant minister for fisheries in northern Somalia's Puntland region, told Reuters.

"I think a ransom was paid but I do not know the exact amount," he added, but gave no other details.

Piracy is rife off Somalia, which has been mired in anarchy since warlords overthrew a dictator in 1991. Maritime officials say at least 30 ships have been hijacked off the coast of Horn of Africa nation so far this year.

A record four ships were seized in 48 hours last week, meaning pirates are holding hostage four cargo vessels, two tankers and a tug boat, along with about 130 crew members. - Reuters