Singapore has sent two warships and a naval helicopter to help in the six-country search for Malaysia Airlines (MAS) flight MH370 that went missing on Saturday.

This is in addition to a military transport plane that was deployed on Saturday, and a rescue submarine - equipped to search underwater and has divers on board - that will be sent on Sunday.

In a post on its Facebook page at about 9am on Sunday, the Republic of Singapore Navy (RSN) said that its missile corvette, frigate and Sikorsky S-70B Seahawk naval helicopter has joined in the search for MAS flight MH370 since 2am on Sunday.

The Sikorsky S-70B Seahawk naval helicopters are able to drop sonar underwater and are attached to the navy's Formidable class of frigates - its most advanced warships that are designed for stealth, speed and manoeuvrability. Its Victory class of missile corvettes are fast attack vessels that the navy calls "the backbone of the RSN's strike capability".

The RSN added that its SSRV MV Swift Rescue submarine, which has been preparing for the operation through the night, will join in later on Sunday.

In a tweet on Sunday morning, the Singapore Army wished them success.

Earlier, on Saturday, a Republic of Singapore Air Force (RSAF) C-130 aircraft took off at noon to assist in the search, which the RSAF, Singapore Rescue Co-ordination Centre and the Civil Aviation Authority of Singapore are helping to coordinate.

Singapore Defence Minister Ng Eng Hen called his counterpart, Malaysia Defence Minister Hishammuddin Hussein, on Saturday night to convey Singapore's sympathies and offer assistance.

On top of the military transport plane, he also offered the use of the rescue submarine, which Mr Hishamuddin accepted.

On Saturday, both Singapore's Chief of Navy, Rear-Admiral Ng Chee Peng, and Chief of Air Force, Major-General Hoo Cher Mou, spoke to their counterparts, the Chief of the Royal Malaysian Navy, Admiral Tan Sri Abdul Aziz Haji Jaafar, and the Chief of the Royal Malaysian Air Force, General Tan Sri Dato Sri Rodzali Daud, to coordinate the details of the Singapore Armed Forces' assistance and offer additional assistance if required.

Malaysia, Vietnam, the Philippines, China and the United States are also involved in the search for the missing plane.

The Boeing 777-200 aircraft, which was bound for Beijing from Kuala Lumpur, took off just after midnight on Saturday, and lost radar contact 50 minutes later.

It was carrying 227 passengers and 12 crew members from 14 countries and Taiwan. There were no Singaporeans on board.

Two giant oil slicks, consistent with the sort that would be left by fuel from a crashed jet, were spotted in the sea off southern Vietnam on Saturday night, but no wreckage has been found.