Moscow has lost communication with the leadership of the Iranian nuclear facility as officials neither answered phone calls nor responded to emails, leaving more than 600 Russian citizens stranded, Director General Alexey Likhachev of Rosatom nuclear power company said on Tuesday.

“Unfortunately, we have lost contact with the leadership of Iran’s entire nuclear industry: they are not answering their phones or responding to emails,” Russian media TASS cited Mr Likhachev as saying.

The director, who said Iran’s uranium enrichment facilities in Fordow and Natanz were struck with missiles, explained there was no way to assess the impact of the damage since officials were not responding to calls and enquiries.

“We still have no idea about the extent of the damage,” said the Rosatom CEO.

As the war between Iran and U.S.-Israeli forces entered its fourth day on Tuesday, Russia fears the Bushehr Nuclear Power Plant may be targeted in an attack that could trigger a regional-scale destruction.

Mr Likhachev explained that the Bushehr Nuclear plant contains “a huge mass of fissile material” that could wipe out an entire region. He urged all parties of the war to exercise restraint.

“We must understand that the reactor is operating at capacity. It contains 72 tons of fuel and another 210 tons of spent fuel. This is a huge mass of fissile material. In the event of a strike, it would certainly be a regional-scale disaster,” Mr Likhachev said.

Speaking to reporters on Tuesday, Mr Likhachev said about 600 Russian citizens were awaiting evacuation at the facility.

“As of today, there are 639 people there; they are Russian citizens. There are no children there. We have managed to evacuate them. Not too many women remain there, but many women don’t want to leave. They want to stay with their husbands during these difficult times,” Mr Likhachev said.