Shocking CCTV footage emerged on social media supposedly showing the jet racing vertically towards the ground in the moments before the smash
The China Eastern Airlines flight nosedived before smashing into the hillside and erupting in a huge fireball near the city of Wuzhou in Teng county in the southern province of Guangxi.
A rescue official reportedly said the plane had completely disintegrated while a fire sparked by the crash burned down bamboo and trees before being put out.
China's Civil Aviation Administration of China (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 said in a statement: 'The CAAC has activated the emergency mechanism and sent a working group to the scene.'
The Aviation Safety Network tweeted: 'We are following multiple unconfirmed reports about a possible accident involving China Eastern Airlines flight #MU5735 a Boeing 737-89P (B-1791) en route from Kunming to Guangzhou, China.'
One villager told a local news site the plane involved in the crash had 'completely fallen apart' and he had seen forest destroyed by the fire caused by the crash.
A Chinese airliner with 133 people on board has crashed in the southern province of Guangxi, erupting in a horror fire across a mountain
But tracking ended at 2.22pm (6.22am GMT) at an altitude of 3,225 feet with a speed of 376 knots. The plane had been cruising at an altitude 29,100 feet at 6.20am GMT, according to FlightRadar24 data.
Just over two minutes and 15 seconds later, the next available data showed it had descended to 9,075 feet. In another 20 seconds, its last tracked altitude was 3,225 feet.
It had been due to land in Guangzhou, on the east coast, at 3.05pm (7.05am GMT).
Shares of Boeing Co were down 6.4 per cent at $180.44 in premarket trade. Boeing did not immediately respond to a request for comment.
The website 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.
Aviation data provider OAG said this month state-owned China Eastern Airlines was the world's sixth-largest by scheduled weekly seat capacity and the biggest in China.
It has had a relatively strong performance in the domestic market during the coronavirus pandemic despite tight curbs on international flights, OAG said.
It is one of China's top three airlines, operating scores of domestic and international routes serving 248 destinations.
The aircraft was delivered to China Eastern from Boeing in June 2015 and had been flying for over six years.
The twin-engine, single aisle Boeing 737 is one of the world's most popular planes for short and medium-haul flights.
China Eastern operates multiple versions of the common aircraft, including the 737-800 and the 737 Max. The 737 Max version was grounded worldwide after two fatal crashes.
China's aviation regulator cleared that plane to return to service late last year, making the country the last major market to do so.
The safety record of its airline industry has been among the best in the world in the past decade.
According to Aviation Safety Network, China's last fatal jet accident was in 2010, when 44 of 96 people were killed when an Embraer E-190 regional jet flown by Henan Airlines crashed on approach to Yichun airport in low visibility.
The 737-800 model that crashed today has a good safety record and is the predecessor to the 737 MAX model that has been grounded in China for more than three years following fatal crashes in 2018 in Indonesia and 2019 in Ethiopia.
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.
Most of the passengers onboard the Malaysia Airlines Flight MH370, which disappeared in March 2014 en route from Kuala Lumpur to Beijing, were from China.
Boeing 737-800's have had a series of deadly crashes in past:
2006: Gol Transportes Aéreos flight broke up and crashed in Brazil with all 154 on board dying
2007: Kenya Airways flight crashed into a swamp on the way to Nairobi with all 108 passengers and six crew dying
2009: Turkish Airlines flight from Istanbul crashes in a field near the Polderbaan while trying to land at Amsterdam's Schiphol Airport with nine people dying
2010: Ethiopian Airlines flight crashed into the Mediterranean Sea after taking off from Beirut, with all 90 passengers and eight crew dying
2010: Air India Express flight overran the runway on landing at Mangalore International Airport, with 158 passengers and six crew dying and just eight survivors
2016: Flydubai flight from Dubai to Rostov-on-Don in Russia crashed on the final approach, with all 62 people dying
2018: Air Niugini flight from Pohnpei, Federated States of Micronesia, to Port Moresby, Papua New Guinea, with a stop-off at Chuuk International Airport, undershot the runway and landed in a lagoon, with one person dying
2020: Ukraine International Airlines flight crashed shortly after taking off from Tehran bound for Kyiv with no survivors among the 167 passengers and 9 crew
2020: Pegasus Airlines flight skidded off the runway at Istanbul Sabiha Gökçen Airport before splitting into three pieces of fuselage, leaving three dead
2020: Air India Express flight overshot the runway while landing in heavy rain and crashed into a gorge at Calicut International Airport, with both pilots and 18 passengers dying
2022: China Eastern Airlines flight crashed while en-route to Guangzhou, China
With lift-creating wings, airplanes tend to go down in corkscrew-like trajectories.