MOSCOW -- A total of 23 Russian citizens were aboard a Greek-owned oil tanker seized by pirates in Togolese waters, the Russian Foreign Ministry said Wednesday.

"The Greek ship owner has reported that there are 23 Russian citizens and one Greek citizen, the captain, on board the ship. The ship owner got in touch with the captain shortly after the attack and learned that the crew members' lives are not in danger, " the ministry said in a statement.

The Russian Embassy in Benin and Togo has reported Togo's coast guard boats have chased the seized tanker, but failed to catch it, the ministry said, adding preliminary information showed the ship was now in international waters far from Nigeria.

"The Russian embassies in the region and local authorities are taking all necessary measures to ensure the security of Russian citizens on board the tanker," the ministry said.

The Greek-owned oil tanker with 24 crew members aboard was seized only miles off the Togolese capital Lome on Tuesday morning.

It was at least the second major attack by pirates in less than two weeks in the oil-rich Gulf of Guinea, running from Guinea on Africa's northwestern tip to Angola in the south.