Haixun 01, searching for the Malaysia Airlines Flight MH370, detected a pulse signal with a frequency of 37.5kHz per second in southern Indian Ocean waters today, state-run Xinhua news agency reported.
It is yet to be established whether it is related to the Boeing 777-200, that went missing on March 8 with 239 people on board, including five Indians.
The batteries of the black box flight recorders have a life of about 30 days, meaning they will shut down in the next three days.
Officials said the multinational team has entered the most intensive phase in the search operations.
Up to 10 military planes, three civil jets and 11 ships were searching about 217,000 sq km, 1,700 km north west of Perth, to locate the plane's data recorder that could help investigators unravel the mystery of what happened on March 8, the day the Beijing-bound jet suddenly disappeared from radar screens.