Use of force
Word of the latest attack at sea came 10 days after Somali pirates had seized the Sirius Star, a Saudi supertanker, in the largest hijacking in maritime history.
The group of pirates had originally demanded $25 million to release the ship, which was captured at least 450 nautical miles southeast of Kenya, but cut their ransom to $15 million.
The capture of the Sirius Star on November 15, with $100 million of oil and 25 crew members from Britain, Poland, Croatia, Saudi Arabia and the Philippines, focused world attention on rampant piracy off the coast of Somalia.
Scores of attacks this year have brought millions of dollars of ransom payments, hiked up shipping insurance costs, sent foreign navies rushing to the area, and left about a dozen boats with more than 200 hostages still in pirates' hands.
Following the hijack of an Iranian-chartered ship last week, Ali Taheri, Iran's deputy transport minister, said Tehran could use force if necessary against pirates.
"Iran's view is that such issues should be confronted strongly," he said.
The Gulf of Aden is linked to the Red Sea, an area that has earned its reputation as the world's most dangerous waterway where at least 95 pirate attacks have taken place this year and 39 ships have been hijacked.
At least 15 of those ships carry almost 300 crew still in the hands of Somali pirates.