Two members of the Russian doomsday cult that have been hiding in a cave to wait for the end of the world have reportedly died, the first fatalities since the group went underground five months ago.

One member of the religious sect, Vitaly Nedogon, who left the cave last week, said that both were women and that one had died from cancer and another had starved herself to death.

Officials in the Penza region were continuing efforts to persuade the remaining members to return above ground amid fears that the cave near the village of Nikolskoye is in imminent danger of collapse.

The task has been complicated by the group's decision to take a vow of silence while they wait for the Apocalypse. Penza's deputy governor Oleg Melnichenko, who is leading the effort, told Interfax that he had no information about any deaths among those underground.

Nedogon told Russian television: "Two people died while in the bunker, they are buried there. One woman called Tamara died of cancer. The other woman from Belarus died while fasting."

Anton Sharonov, spokesman for Penza's regional administration, said it was impossible to verify the claim until the remaining members of the sect left the cave.

"Therefore, Vitaly Nedogon's statement is now being treated as testimony that has not been proven so far," he said. "Negotiations are suspended because the sect members are keeping a vow of silence. The official number of those in seclusion is 11 people." The doomsday sect is a splinter group from the Russian Orthodox Church and its adherents believe that the world will end in May. They reject processed food and consider bar codes to be satanic symbols.

Thirty-five members entered the cave at the beginning of November and threatened to blow up gas canisters blocking the entrance if the authorities tried to force them out.

Their leader, Pyotr Kuznetsov, 43, did not join his followers underground. He attempted suicide last week by hitting himself over the head with a log, apparently after realizing that his prediction of the Apocalypse was wrong.

The bearded guru has been diagnosed with schizophrenia but officials brought him from a psychiatric hospital to Nikolskoye, 435 miles south east of Moscow, so that he could persuade his followers to leave the cave. Kuznetsov was present when a woman emerged with two children last Wednesday.

Nedogon was among 14 who were forced to abandon the cave a day earlier when part of the roof collapsed under the pressure of spring floodwater. Seven women left the bunker at the end of March.

The remaining members of the group have previously agreed to end their vigil on April 27, when the Russian Orthodox Church marks Easter. Many of the former cave-dwellers continue to wait for the end of the world at Kuznetsov's wooden cottage in Nikolskoye, regardless of his suicide attempt.