An explosion at a steel production complex in central Iran killed seven workers including foreigners, the semi-official Fars news agency quoted a senior local official in Yazd province as saying on Monday.

"The explosion at the Ghadir Steel plant led to the deaths of seven people and the serious injuries of 12 others who have been transferred to hospital for treatment," said Yazd's governor Azizulah Seifi.

"It happened on Sunday and caused the death of a number of foreign workers," he said, without elaborating on the number and nationality of the foreigners killed.

Seifi said the cause of the explosion had not been unidentified and an investigation was under way.

"The plant belongs to the private sector and its directors and officials have been summoned... experts are trying to determine the cause of the incident," Seifi said.

Last month, a mysterious blast rocked Isafahn in western Iran and reportedly damaged a key nuclear facility in the city.

Haaretz cited Iranian media as reporting that an explosion was heard near Isfahan, home to a uranium conversion plant operational since 2004.