Greenpeace is criticizing Spain's government for towing a burning Russian fishing boat full of fuel out to sea after it caught fire in a Canary Islands port, saying the fuel oil in the ship that ended up sinking poses an environmental threat.

The group demanded Thursday that Spain make plans to extract about 1,400 metric tons of thick fuel oil from the Russian trawler Oleg Naydenov.

It caught fire in port Saturday and was towed to sea as a precaution.

The ship sank Tuesday night in waters 2,400 meters (7,900 feet) deep, 24 kilometers (15 miles) south of Gran Canaria island.

Development Minister Ana Pastor is on Gran Canaria to oversee oil spill monitoring efforts.

Some oil slicks were spotted drifting southwest and away from the island.