Somali pirates have seized a Ukrainian ship carrying at least 30 tanks and some Russian crew, a maritime group said on Friday, and Russia announced it was sending a warship to the region to combat piracy.

The U.N. World Food Programme said Canada had also extended its vital naval escorts of food aid shipments for another month.

Pirates have captured more than 30 vessels off Somalia this year, making its waters the most dangerous in the world and threatening a globally important shipping lane between Europe and Asia. The gangs seek, and often get, large ransoms.

The East African Seafarers' Assistance Programme said the Ukrainian ship seized on Thursday was carrying tanks. Ukrainian news agency Interfax-Ukraine also said the ship, under a Belize flag, had a military cargo "including about 30 T-72 tanks".

That would be a significant seizure in Somalia, where Islamist insurgents have been battling for nearly two years against the government and its Ethiopian military ally.

Although under a U.N. arms embargo, the Horn of Africa nation is awash with arms. Reports the tanks had been taken also raised questions about their original planned destination.

"Some say it was carrying about 38 tanks, others say 30," said Andrew Mwangura, of the Mombasa-based East African Seafarers' Assistance Programme.

"In the past, military equipment has come through Mombasa on its way to south Sudan, but we have not seen any south Sudanese officials at the port waiting. And anyway, there is an arms embargo for Sudan."