In a move that could change the pirate-hostage equation, Somali pirates on Friday took in a multimillion-dollar ransom, then released the ship and some of the crew but kept all the Indian crew members as hostages.
The pirates said they had freed the tanker MT Asphalt Venture after receiving $3.6 million, but this could not be independently verified.
"We have received $3.6 million early this morning for the release of the tanker," said a pirate calling himself Ahmed.
"The ship has just sailed away but we have taken some of its Indian crew back because the Indian government is currently holding our men. We need the Indian government to free our men so that we can release their citizens."
Another pirate told The Associated Press the Indian crew members' hostage ordeal is being prolonged in retaliation for the arrests of more than 100 Somali pirates by the Indian navy.
"We decided to keep the Indian because India is holding our colleagues," the pirate, Hassan Farah, said. "We released the other crew members who sailed away from our coast. We will keep these Indians until the Indians release our colleagues."
Farah said the pirates in the stronghold of Haradhere have taken that collective decision. The Indian hostages are to be moved to land.
Pirates are receiving an average of $5 million to release ships and crew, and a ransom in that ballpark was believed to have been paid on Friday for the release of the Asphalt Venture, whose ownership is located in Mumbai, India.
It wasn't immediately clear how many of the 15 crew members aboard the Asphalt Venture were Indian. The ship was hijacked in late September.
Friday's pirate action marks a major departure from the standard pirate business model of release-for-ransom and could complicate international military efforts against the piracy trade.
Earlier this year pirates killed four American hostages while U.S. Navy warships were shadowing the hijacked yacht, the first time pirates had done that.
Overall, analysts say pirates are becoming increasingly aggressive, violent and hostile.
The Indian navy has seized around 120 pirates, mostly from Somalia, over the past few months. Last month the Indian navy captured 61 pirates when they attacked a naval ship. Indian warships have been escorting merchant ships as part of international anti-piracy surveillance in the Indian Ocean area since 2008.
Piracy has long plagued the shipping industry off East Africa, but violence has escalated in recent months. Pirates held some 30 ships and more than 600 hostages.