China launched a secret reconnaissance satellite with a Long March rocket Monday, the sixth satellite it has launched this year, authorities said.

The mission lifted off aboard a Long March 4C rocket from the Taiyuan launching center in northern China's Shanxi province, SPACE.com reported.

Independent tracking data showed the three-stage booster placing the satellite in an orbit about 380 miles high.

The state-run Xinhua news agency said the satellite would conduct scientific experiments, make land surveys, estimate crop yields and help respond to natural disasters.

But observers say it is likely a military high-resolution optical and radar reconnaissance satellite, SPACE.com said.

The Yoagon series of satellites began launching in 2006, and a recent launch in March included three spacecraft believed to be naval observation satellites.

In a move typical of China's policy regarding military payloads, the launch was announced less than 24 hours in advance, SPACE.com said.