Later, Aleksandr Bastrykin, the head of the Investigative Committee, said that they “urgently” needed to take eyewitness evidence from the crew members.

“We do not rule out that the ship might have been carrying something other than timber. So we had to detain part of the crew – in order to find out if anyone was involved in the hijacking,” Bastrykin told journalists.

Arctic Sea, supposedly transporting timber from Finland to Algeria, was seized on July 24 in the Baltic Sea. It was only on August 17 that the vessel was discovered 300 miles off Cape Verde.

Meanwhile, the suspected hijackers of the cargo ship deny Russia's charges of piracy and kidnapping, insisting they are ecologists and were trying to save themselves after they ran out of fuel.

Among the alleged pirates are citizens of Estonia, Latvia and Russia.