China will give unusually large payouts to the families of firefighters killed in giant explosions in Tianjin last month, local media reported, after the disaster raised questions over whether the young men's training was inadequate.

Each family will receive 2.3 million yuan ($360,000) in compensation, a payment that includes extra money for "martyrdom", the Beijing News reported late Wednesday.

The death toll from a series of explosions on August 12 rose to 164 on Thursday, Tianjin authorities said, 97 of them firefighters. Nine people are still missing.

The compensation amount is more than double the $145,000 given to the families of each of the victims of a 2011 train crash outside the city of Wenzhou.

Of the 2.3 million yuan, 940,000 yuan is a "martyrdom payment", while most of the rest is 30 times the average annual urban salary, for lost income due to death.

The standard compensation for accident victims in China is 20 times the average salary.

The relatively large amount may be an attempt by the authorities to quell criticism after questions were raised over whether poorly trained firefighters could have contributed to the detonations in Tianjin.

Reports said emergency workers responding to a blaze at a hazardous goods storage facility could have sprayed water over calcium carbide, listed as being at the site. The two substances react to produce highly combustible acetylene gas.

Nearly all of China's firemen are contract labourers -- young, poor men from the countryside who receive limited training, provoking public concern over the professionalism and capabilities of the service.