South Korea ordered a warship to chase a cargo ship hijacked by suspected Somali pirates over the weekend, a Seoul official said Sunday, as President Lee Myung-bak urged "all possible measures" to rescue the 21 crew members.

The Choi Young destroyer was sent to pursue the Samho Jewelry, a 11,500-ton South Korean chemical freighter seized in the Indian Ocean, a presidential spokeswoman said.

Lee held an emergency meeting Sunday and urged officials to take "all possible measures" to rescue the ship and crew, she said.

Samho Jewelry was carrying eight South Koreans, two Indonesians and 11 crewmembers from Myanmar when it was hijacked on its way from the United Arab Emirates to Sri Lanka.

All crewmembers being held by the pirates have been confirmed safe, a foreign ministry spokesman said.

"The crewmen have been confirmed safe for now, with no unusual signs in their (physical) conditions. ... The ship's location has been identified," the spokesman told AFP.

Saturday's hijacking came two months after Somali pirates released a supertanker belonging to the same South Korean shipping company after the ship was held for seven months.