A China Eastern Airlines aircraft with 132 people on board crashed in mountains in south China on Monday while on a flight from the city of Kunming to Guangzhou, China's Civil Aviation Administration of China (CAAC) said.

The jet involved in the accident was a Boeing 737 aircraft and the number of casualties was not immediately known, state broadcaster CCTV said. Rescue was on its way, it said.

There was no word on the cause of the crash of the plane, a 6-year-old 737-800 aircraft, according to Flightradar24.

The CAAC said the aircraft lost contact over the city of Wuzhou. It had 123 passengers and nine crew on board. State media said earlier there were 133 people on board.

"The CAAC has activated the emergency mechanism and sent a working group to the scene," it said in a statement.

The flight departed the southwestern city of Kunming at 1:11 p.m. (0511 GMT), FlightRadar24 data showed. The flight tracking ended at 2:22 p.m. (0622 GMT) an altitude of 3225 feet with a speed of 376 knots.

It had been due to land in Guangzhou, on the east coast, at 3:05 p.m. (0705 GMT).

The web site of China Eastern Airlines was later presented in black and white, which airlines do in response to a crash as a sign of respect for the assumed victims.

The safety record of China's airline industry has been among the best in the world over the past decade.

According to Aviation Safety Network, China's last fatal jet accident was in 2010, when 44 of 96 people on board were killed when an Embraer E-190 regional jet flown by Henan Airlines crashed on approach to Yichun airport in low visibility.

In 1992, a China Southern 737-300 jet flying from Guangzhou to Guilin crashed on descent, killing all 141 people on board, according to Aviation Safety Network.

Chinese President Xi 'shocked' over plane crash; orders 'all-out search' and rescue efforts

Chinese President Xi Jinping said that he was shocked to learn about the crash of a passenger plane with 132 people aboard on Monday and ordered an all-out search and rescue efforts.

The Boeing 737 aircraft of China Eastern Airlines, which flew from Kunming to Guangzhou, crashed in Tengxian County in the city of Wuzhou in the southern Guangxi Zhuang Autonomous Region, causing a mountain fire.

In his instructions issued soon after the incident, Xi said he was shocked to learn about the incident involving China Eastern Airlines flight MU5735 from Kunming to Guangzhou,

He ordered the immediate launch of emergency response, all-out search and rescue efforts and proper settlement of the aftermath, state-run Xinhua news agency reported.

He said swift action should be taken to identify the cause of the crash and to strengthen the safety overhaul of the civil aviation sector to ensure the absolute safety of the sector and people's lives.

State-run CGTN reported that the first rescue team has reached the crash site in the remote mountains.

Meanwhile, China Eastern Airlines changed the colour of its website to black as it prepared to announce the casualties in the crash.

With inputs from KJM Varma (PTI)