"No submarine is coming from our friendly country. What they are sending is what we called submarine escape rescue vessel," he said, in clearing the air over the concern by some parties that foreign submarines were entering Malaysian waters.

In a post on its Facebook page at about 9am Sunday, the Republic of Singapore Navy said that its frigate, missile corvette and Sikorsky S-70B naval helicopter has joined in the search for MAS flight MH370 since 2am, while the SSRV MV Swift Rescue submarine, which had been preparing for the operation through the night, would join in later.

Jen Zulkefli said Malaysian Royal Navy was also deploying its submarine escape rescue vessel.

"The two type of assets are a totally different things," he said in a press conference Sunday to update the media on the operation.

It is learnt that the Malaysian Scorpène-class submarine was not deployed in the operations as it was not designed for search and rescue missions.

Jen Zulkefli said a total of 34 aircrafts and 40 vessels were involved in the operation.