Spain investigates sinking of fuel-laden ship off Canary Islands

The Oleg Naydenov, a Russian fishing trawler full of fuel, which caught fire over the weekend in Gran Canaria's port of Las Palmas, can be seen in this handout picture taken April 12, 2015. REUTERS/Salvamento Maritimo/Handout via Reuters

MADRID (Reuters) - Spain launched an investigation on Thursday into the sinking of a Russian ship off the Canary Islands, as coastguards battled a six-km (3.7-mile) oil slick close to tourist beaches.

Environmentalist group Greenpeace criticised authorities for towing the burning fishing vessel out to sea after it caught fire in Las Palmas port early on Sunday.