DHAKA: Australian prime minister Tony Abbott said on Sunday searchers were ‘hopeful but by no means certain’ that a pulse signal reportedly detected by a Chinese ship in the Indian Ocean was related to a Malaysia Airlines jetliner missing for four weeks.

Chinese state news agency Xinhua reported that a patrol vessel hunting for Flight MH370 had picked up a ‘ping’ on Saturday, raising hopes that it could be from the underwater beacon of the plane’s ‘black box’ voice and data recorders.

Australian search authorities said such a signal would be consistent with a black box, but both they and Xinhua stressed there was no conclusive evidence linking it to the Boeing 777 that went missing on March 8 with 239 people aboard shortly after taking off from Kuala Lumpur for Beijing.

‘This is the most difficult search in human history. We are searching for an aircraft which is at the bottom of a very deep ocean and it is a very, very wide search area,’ Abbott told reporters in Tokyo, where he is on a visit, reports The Straits Times.

‘We need to be very careful about coming to hard and fast conclusions too soon.’

Up to a dozen planes and 13 ships will be scouring three separate areas about 2,000 km northwest of Perth, Australia`s Joint Agency Coordination Centre said on Sunday.

A black box detector deployed by Chinese vessel Haixun 01 picked up the ‘ping’ signal with a frequency of 37.5kHz per second, the same as emitted by flight recorders, at about 25 degrees south and 101 degrees east, Xinhua said.

‘The 37.5kHz is the specific frequency that these locator pingers operate on,’ said Anish Patel, president of Sarasota, Florida-based Dukane Seacom, which made the black box locator.

BDST: 1507 HRS, APR 06, 2014