The Chinese State news agency has said a Chinese patrol vessel has discovered a pulse radio signal in the Indian Ocean.

Crews searching for the missing Malaysia Airlines jet launched a targeted underwater hunt for the plane’s black boxes, with just days left before the devices’ batteries are expected to run out.

Malaysia’s prime minister has said the search for the missing airliner will not stop until answers are found, as his Australian counterpart called it “the most difficult in human history”.

Investigators are conducting a forensic examination of the final recorded conversation between ground control and the cockpit of Malaysia Airlines Flight 370 before it went missing three weeks ago, the Malaysian government said.

A cluster of orange objects spotted by a search plane hunting for any trace of the missing Malaysia Airlines jet turned out to be nothing more than fishing equipment, Australian officials have said.