Russian media said the six injured people were fighting for their lives following the Thursday evening fire at the Kamensky chemical plant in the southern Rostov region, which they described as an arms production plant.

"As a result of the incident, seven people received burns," said the ministry of trade and industry which oversees the plant.

"Unfortunately, one man died," the ministry said in a statement to AFP.

The plant, which is located in the town of Kamensk-Shakhtinsky, released a terse statement saying seven workers were hospitalised.

Neither the plant nor the ministry provided any information on the severity of the injuries.

But Russian news agencies, citing informed sources, said the six workers were in critical condition.

"Doctors are fighting for their lives," an informed source told news agency Interfax.

The plant stressed that the fire had been swiftly put out and "no harmful emissions had been released into the atmosphere."

Authorities launched a probe which is headed by an official who is in charge of production of conventional arms and ammunition at the ministry of industry and trade.

The plant, which describes itself as working to strengthen Russia's defence capabilities, declined to provide further comment.

Officials in Kamensk-Shakhtinsky and the chief doctor of the local hospital, which is treating the workers, declined to comment.

"Neither I, nor my staff will speak to you," the doctor told AFP.

The ministry of industry and trade implied that the workers violated safety regulations.

"The technological operation during which the fire occurred is highly automated and does not foresee the presence of people on the shop floor," the ministry said in a statement.

Interfax said that the fire started because workers at the plant violated safety rules while handling "chemical reagents."

Dmitry Kapranov, the ministry official in charge of the probe at the plant, was not available for comment.

His assistant said he had left for Kamensk-Shakhtinsky Thursday evening.