At least 44 people are dead and another 400 are injured, according to state broadcasters, after multiple huge explosions rocked the Chinese port city of Tianjin.

Twelve firefighters are reportedly among the dead and 32 of those injured are in critical condition.

The explosions, so large they could be seen by satellites in space, reportedly began at around 11:30pm (3:30pm GMT) in the Binhai district, and shattered windows and knocked off doors of buildings in the area, Beijing News reported.

The explosion occurred at a warehouse for explosive and dangerous goods. Xinhua News said the first explosion was equivalent to 3 tons of TNT, and the second, 21 tons.

The blasts then triggered others at nearby businesses, according to Xinhau.

One thousand firefighters were called to tackle the blazes, according to Xianhau.

The state-run Beijing News cited Tianjin fire authorities as saying they had lost contact with 36 firefighters, and that another 33 were among the hundreds of people being treated in nearby hospitals.

It is not yet known what caused the explosion, but videos from the scene show a dramatic fireball exploding near the site of a fire.

As dawn broke, images emerged of hundreds of burned-out vehicles at the site of the explosion.

President Xi Jinping demanded that authorities "make full effort to rescue and treat the injured and ensure the safety of people and their property".

Xi said in a statement carried by official media that those responsible should be "severely handled".

Burned-out cars lined the streets of Tianjin (Reuters)

Residents reported feeling a huge shockwave after the explosion.

Photos circulating online show a gigantic fireball high in the sky, with a mushroom-cloud.

This mobile phone picture shows people on the street in the aftermath of the explosion (AFP/Getty)

Video posted on YouTube from what appeared to be an apartment building some distance from the scene showed an initial blast followed by a second, much bigger, explosion. Shockwaves hit the building seconds later.

"Our building is shaking. Is this an atomic bomb?" said a frenzied voice inside.

Tianjin Explosion - In Pictures Show all 14 1 /14 Tianjin Explosion - In Pictures Tianjin Explosion - In Pictures Tiajin Explosion A man wearing a mask walks past overturned shipping containers after explosions hit the Binhai new district in Tianjin. Two massive explosions caused by flammable goods ripped through an industrial area in the northeast Chinese port city of Tianjin late on Wednesday, killing 17 people and injuring around 400, official Chinese media reported. Tianjin Explosion - In Pictures Tianjin8.jpg A screen grab from taken from state broadcaster China Central Television (CCTV) footage on August 12, 2015 shows a huge explosion in the northern Chinese port city of Tianjin. Tianjin Explosion - In Pictures Tianjin Explosion Excavators work near the site of the explosions at the Binhai new district, Tianji Tianjin Explosion - In Pictures Tianjin Explosion A man who was injured following the massive explosions at the Binhai new district in Tianjin receives medical treatment at a hospital. Tianjin Explosion - In Pictures Tianjin Explosion View of the destruction after explosions in the port area of Tianjin, northern China, Tianjin Explosion - In Pictures Tianjin Explosion A emergency worker is lifted by a crane as smokes plumes from the explosion site in Binhai new district in Tianjin Tianjin Explosion - In Pictures Tianjin Explosion A damaged truck is seen on a highway near the site of the explosions at the Binhai new district in Tianjin Tianjin Explosion - In Pictures Tianjin Explosion Flames rise as a banner in the background reads "no illegal operations" at the site of a series of explosions in Tianjin, witnesses described a fireball from the blasts ripping through the night sky. Tianjin Explosion - In Pictures Tianjn Explosion Smoke rises from shipping containers after explosions at Binhai new district in Tianjin, China. Tianjin Explosion - In Pictures Tianjn Explosion Firefighters take a break after trying to put fire down at the explosion site in Binhai new district in Tianjin, Tianjin Explosion - In Pictures Tianjn Explosion A survivor talk on his mobile phone at the site of the explosions at the Binhai new district in Tianjin Tianjin Explosion - In Pictures Tianjin Explosion Firefighter's truck and other rescue vehicles are pictured as smoke rises among shipping containers after explosions at Binhai new district in Tianjin Tianjin Explosion - In Pictures Tianjn Explosion Damaged cars are seen near the site of explosions at the Binhai new district in Tianjin Tianjin Explosion - In Pictures Tianjn Explosion A paramilitary policeman wears a mask as he blocks the road leading to evacuated residential area and the explosion site in Binhai new district in Tianjin

Local residents in Tianjin are posting pictures of shattered windows and injured people.

Cars burning during the blaze in Tianjin (Reuters)

State broadcaster CCTV says six battalions of firefighters had brought the ensuing fire under control, although it was still burning. It says the firefighters were combing the neighbourhood for possible injured residents.

Tianjin resident Zhang Siyu, whose home is several kilometres from the blast site, told the Associated Press: “I thought it was an earthquake, so I rushed downstairs without my shoes on.

“Only once I was outside did I realize it was an explosion. There was the huge fireball in the sky with thick clouds. Everybody could see it.”

She said she could see wounded people weeping. She said she did not see anyone who had been killed, but added: “I could feel death.”

Han Xiang, who lives in the city, compared the blast to an earthquake but said “then there was a huge mushroom cloud, so we thought we were also in a war.”

Firefighters battling the blaze in Tianjin (Reuters)

Xianhua identified the owner of the warehouse involved in the first explosion as Tianjin Dongjiang Port Ruihai International Logistics. The company's website said it was a government-approved firm specialising in handling "dangerous goods". Company officials could not immediately be reached for comment.

According to an assessment by government environmental inspectors published in 2014, the facility was designed to store several dangerous and toxic chemicals including butanone, an explosive industrial solvent, sodium cyanide and compressed natural gas.

CCTV said at least one person at a "relevant company" had been detained.

Tianjin is a major port and industrial area, around 70 miles from the capital Beijing and home to around 15.2 million people.