Ships searching the Indian Ocean for a Malaysian airliner have detected three separate underwater signals, and more ships and planes have been diverted to investigate whether they could have come from its “black box”.

Angus Houston, head of the Australian search mission, said the detections were being taken “very seriously” as time ticked down on the battery life of the black box’s tracking beacons.

He said China’s Haixun 01 has twice detected an underwater signal on a frequency used for the plane’s flight data and cockpit voice recorders – once for 90 seconds on Saturday and another more fleeting “ping” on Friday, a short distance away.

A third “ping” was also being scrutinised, 300 nautical miles away in the Indian Ocean.

The Malaysia Airlines Boeing 777 with 239 people aboard vanished on March 8 during a flight from Kuala Lumpur to Beijing.

“This is an important and encouraging lead but one which I urge you to continue to treat carefully,” Houston told reporters.

“We are working in a very big ocean and within a very large search area.”

A spokeswoman for Britain’s Ministry of Defence confirmed late on Sunday that the HMS Echo, equipped with a black box locator, had arrived in the area where the Chinese had reported a ping.

“It will start its work to find the black box in the next hour,” the spokeswoman told AFP.

Earlier, Houston said Australian ship Ocean Shield – also equipped with a black box locator – and Australian air force planes were being diverted to the area to help discount or confirm the Chinese signals.

Ocean Shield was also investigating the signal it detected on Sunday in its current location, about 300 nautical miles north of Haixun 01, in waters far off Australia’s west coast.

Houston said the Chinese finding was more promising.

“I think the fact that we’ve had two detections, two acoustic events in that location, provides some promise which requires a full investigation,” he said.