Pirates have hijacked an oil tanker off the Nigerian coast, taking three hostages and killing the vessel's Greek deputy commander, a spokeswoman for the Greek coastguard said Wednesday.

The Malta-flagged Kalamos, which has a crew of 23 including 10 Greeks, was anchored off the coast and awaiting fresh cargo from Qua Iboe, a terminal in Nigerias southeastern region, when it was boarded on Tuesday, she said.