At least 29 people were killed and dozens of others injured in a fire that ripped through a hospital in China's capital Beijing, a city official confirmed Wednesday.

The fire at the Beijing Changfeng Hospital in the Fengtai District broke out at around 1 p.m. (5 a.m. GMT) Tuesday and was extinguished about half an hour later.

Li Zongrong, deputy mayor of the district, expressed his "deep condolences" as he announced the new toll at a press conference.

Twelve people, including the facility's director, have been detained in connection with the fire, said Sun Haitao from Beijing's public security bureau, adding that representatives from a company renovating the hospital were among those being held.

State broadcaster CCTV reported that a preliminary probe revealed the blaze had been caused by "sparks generated during the internal renovation and construction of the inpatient department of the hospital."

The sparks "ignited the volatiles of the flammable paint on the site," CCTV said.

Social media users posted videos Tuesday of people sitting on external air conditioning units, while others clinging to ropes jumped from the building.

The victims were 16 women and 13 men, Li said.

"We feel deep remorse and guilt," he told journalists.

"On behalf of the Fengtai district party committee and district government, I hereby express our deep condolences for the victims, and express our sincere respects to the victims' families, the injured and their relatives, and apologise to the people of the whole city."

39 hospitalized

CCTV reported that out of the 29 dead, 26 were patients at the hospital, two were hospital staff and one was a patient's family member.

There were still 78 patients being treated at the hospital, who have been moved to the facility's west building, CCTV said.

State-run People's Daily reported that as of Wednesday morning 39 people were being treated in the hospital with injuries, and another three had been discharged.

Top city officials visited the hospital shortly after the fire, with Beijing party secretary Yin Li vowing to "quickly identify the cause of the accident and hold the relevant responsible persons accountable," according to the Beijing Daily.

AFP journalists on Wednesday saw dozens of onlookers outside the entrance to the hospital, where a large number of police officers were stationed, discouraging people from taking photos.

Some of the hospital's windows appeared blackened and at least one was broken, with soot marks visible on parts of the facade.

Many family members have lost contact with patients, with the missing being mostly older people with mobility problems, the China Youth Daily said in a separate report on Wednesday.

A police officer on the scene on Wednesday told AFP the city "will probably make the appropriate arrangements" to take care of victims' relatives.

Beijing Changfeng Hospital is located in the capital's western urban area, about 25 minutes by car from Tiananmen Square.

Deadly fires are common in China due to weak safety standards and lax enforcement.

Ten people died in an apartment block blaze in northwestern Xinjiang in November, sparking protests against COVID-19 lockdowns blamed for hindering rescue efforts.

And 38 people were killed in a fire at a factory in central China, also in November, with authorities blaming workers for illegal welding.