Nairobi- Somali pirates have seized another tanker just days after US and French forces killed five pirates in two separate operations to free hostages, maritime officials said Tuesday.

The East African Seafarers' Association said the MV Irene E.M. was taken overnight, but could give no further details.

The EU Maritime Centre reported that the 22-man crew of the 35,000-ton Greek vessel were unhurt.

Pirate activity has picked up in recent weeks after a lull in activity due to bad weather. Almost 20 ships have been attacked in the last three weeks.

The captain of the Maersk Alabama, Richard Phillips, was freed on Sunday after a five-day standoff with the US Navy. Snipers killed three pirates guarding Phillips on the Alabama's lifeboat.

On Friday, the captain of a French yacht and two pirates died when French naval forces stormed the boat, freeing four hostages.

In 2008, pirates seized more than 40 vessels in and around the Gulf of Aden and collected tens of millions of dollars in ransoms, prompting the international community to send warships to the region.

Around 15 warships from the European Union, a US-led coalition task force and individual countries such as Russia, India and China patrol an area of about 2.85 million square kilometres.