A Russian doomsday cult sheltering in a bunker say credit cards and food packaging bar codes are satanic, the official negotiating the release of children from the group said on Monday. Around 30 followers, including four children, from across Russia and neighboring Belarus met last October and barricaded themselves into a hillside to escape an apocalypse their preacher says is looming in either April or May. "For us right now, what's most important is the children," said Alexander Yelatontsev, an official from Russia's Penza Oblast region, who has been the chief point of contact for the cult since the siege began. "They have burned their passports and say that all plastic (credit) cards and strip codes on food packaging are the work of Satan," he told reporters. Yelatontsev said the people underground were in contact with him regularly, and would accept food only if it had not been processed with modern factory equipment. "Right now they are asking for a cow so that they can have fresh, boiled milk that is not processed," he said. He said progress was slow but local authorities were negotiating with the group to leave their refuge. "In as much as their beliefs have been formed over a long period of time, convincing them to come out is not going to happen quickly," he said. Local residents said the bunker was a pre-revolutionary convent, with a well, a kitchen and areas for sleeping and praying. On Friday the entrance to the bunker partially collapsed after rain and melting snow soaked the muddy hillside and the ground gave way.