JAKARTA (REUTERS) - The black box flight recorders of an AirAsia jet that crashed last month must be analysed in Indonesia, Minister for Maritime Affairs Indroyono Soesilo said on Wednesday, as Jakarta dispatched an unmanned underwater vehicle to recover the tail of the plane.

"The tail is the location of the black box. Hopefully not very long before the black box can be discovered," Mr Soesilo said in a media briefing after his arrival in Pangkalan Bun, a town on the island of Borneo with the airstrip closest to the crash site.

"Black box must be read in Indonesia," he said. "Six vessels are at the spot where we found the plane's tail, operating within a radius of 2 nautical miles to do further searches."

His comments came after the tail of flight QZ8501 has been found upturned on the sea bed about 30km from the plane's last known location.

The passenger jet vanished from radar screens over the northern Java Sea on Dec 28, less than half-way into a two-hour flight from Indonesia's second-biggest city of Surabaya to Singapore. There were no survivors among the 162 people on board.

"We've found the tail that has been our main target," Fransiskus Bambang Soelistyo, head of Indonesia's search and rescue agency, told a news conference in Jakarta.

The tail was identified by divers after it was spotted by an underwater machine using a sonar scan, Mr Soelistyo said. He displayed underwater photographs showing partial lettering on the sunken object compared with a picture of an intact Airbus A320-200 in AirAsia livery.

"I can confirm that what we found was the tail part from the pictures," he said, adding that the team "now is still desperately trying to locate the black box".