In a new upsurge in piracy off the Somali coast, two more ships have been hijacked in the past two days.

The European Union's Maritime Security Centre reports that a 32,000 tonne Italian-operated bulk carrier was seized early Monday morning in the Gulf of Aden. "Few details are known at this stage, but the mixed nationality crew are believed to be safe," the centre said.

On Saturday the centre said a 20,000 tonne German container ship was hijacked 400 miles from Kismayo. "The attack was made by six men in a single skiff that was probably operating with other pirate vessels," the centre reported. "The 24-man crew is believed to be safe."

The new reports of piracy followed soon after the International Maritime Bureau's Piracy Reporting Centre had warned of "a spike in pirate activity" off the east coast of Somalia. There had been 15 attacks in the region in March, the bureau said.

On the night of March 31, a chemical tanker successfully repelled a pirate attack. Two days earlier, pirates thought to have mistaken a German naval supply ship for a commercial vessel opened fire on the crew, setting off a chase in which forces from seven nations pursued and arrested seven suspected pirates.

Naval warships from the European Union and countries such as the United States, South Korea and China are patrolling shipping lanes off Somalia in an effort to combat the piracy.