Somali pirates have hijacked a bulk carrier in the Indian Ocean, their first successful attack in almost a week, a maritime watchdog and pirate commanders said yesterday.

Andrew Mwangura, of the East African Seafarers Assistance Programme, confirmed the hijacking overnight of the MV Ariana, a large bulk carrier.

He had initially said the ship was British-owned but later said it emerged the vessel had Greek owners and a British agent.

"The crew of 24 is entirely Ukrainian, we believe they are safe," he told AFP. "It was coming from Brazil and headed to the Middle East."

According to an agent for the owners, the ship was believed to be carrying 35,000 tonnes of soya.

Meanwhile pirates in Haradhere, one of the main bases for the ransom-hunting bandits who have been plying the Indian Ocean, said their group had seized another ship late Friday.

"Our boys have captured two ships. One of them is carrying vehicles," said a pirate who asked to be named only Hassan.

Another commander speaking on condition of anonymity from Haradhere confirmed that two ships had been hijacked but there was some confusion on their flag countries and cargo.

The last time Somali pirates seized a Ukrainian ship, it was carrying 33 Soviet-type battle tanks.

The MV Faina's hijacking was one of the longest since Somali piracy surged in 2007. The vessel and its crew were freed in February after a 134-day hostage crisis.

Maritime watchdogs and foreign navies could not immediately confirm the second hijacking.

If they are both confirmed, the latest hijackings would bring to at least 18 the number of ships currently held by Somali pirates in the Indian Ocean and Gulf of Aden.

April saw a surge in attacks owing largely to favourable weather conditions for the pirates, whose ability to board vessels is diminished during the monsoon seasons.