(Repeats Oct 3 story, text unchanged)
* Air strikes hit underground cave hospital near Hama
* Staff temporarily shuts down hospital and evacuates patients
* Medical workers accuse government of using bunker-busting bombs
By Ellen Francis
BEIRUT, Oct 3 (Reuters) - Even entombing the hospital under solid rock tunnelled beneath a mountain was not enough to protect it from bombs dropped by Syria's government or its Russian allies, medical staff say.
Opposition groups built the "central cave hospital" north of Hama to withstand bombardment, tunnelling into a mountain in northwestern Syria for more than a year to bury it below 17 metres of rock.
To some degree it worked: when Russian or Syrian government warplanes bombed it in two waves of air strikes on Sunday, nobody inside the cave was seriously hurt.
But massive bombs wrecked the emergency ward near the entrance, caved in interior ceilings, crumbled cement walls and destroyed generators, water tanks and medical equipment, knocking the underground hospital out of service.
"The mountainous rock, praise God, did not collapse at all," hospital head Abdallah Darwish told Reuters from the area.
Western countries including the United States say Syria's government and its Russian allies are guilty of war crimes for deliberately targeting civilians, aid deliveries and hospitals during a three week escalation of the civil war.
Moscow and Damascus say they target only militants and deny that they have hit hospitals, although several have been hit during the latest bombing campaign, which began after a ceasefire collapsed in September.
According to Darwish, two waves of strikes hit the hospital. The first attack caused a huge blast at the front entrance of the hospital before another big bomb fell nearby, causing staff to panic, Darwish said.
Since launching their latest intensified air campaign, the Russian and Syrian forces have been using much more powerful "bunker-buster" bombs, which residents of opposition-held areas say have the force to bring down entire buildings.
At least one of the bombs dropped on the cave hospital appeared to be a bunker buster because of the force of the blast, said Ahmad al-Dbis, of the Union of Medical Care and Relief Organizations (UOSSM), a coalition of international aid agencies which funds hospitals in Syria including this one. Staff reported the blast caused "something like an earthquake", he said.
Photos showed long cracks around the rocky, dome-shaped ceiling, and hospital rooms covered in the rubble of collapsing walls.
"Nothing is safe anymore when these kinds of weapons are used," al-Dbis said.
Russian Deputy Foreign Minister Gennady Gatilov said on Monday that accusations that Moscow had struck hospitals were "groundless". He said militants were using civilians and "so-called hospitals" as human shields, setting up medical facilities in cities without correctly marking them.
The Russian Defence Ministry did not immediately reply to a message seeking comment about the specific incident.
A Syrian military source reiterated government denials that hospitals have been targeted. However, the source said militants were being targeted wherever they were, "on the ground and underground".
Since the ceasefire collapsed, fierce battles have been waged in the northern city of Aleppo, where pro-government forces are trying to capture the last major urban area under rebel control, and near Hama, where rebels have launched an advance of their own that threatens to approach the important government-held city.
The cave hospital opened north of Hama in late 2015 after aid groups and other donors paid about half a million dollars to build and equip it. It is close to a frontline where clashes and heavy bombardment have occurred in recent days.
"It was hit at the height of our work, at a time when there was the largest number of patients and wounded," al-Dbis said.
All medical staff and patients were evacuated while equipment was put into storage for fear of another attack on the hospital, he said, describing it as the best fortified in all of rebel-held Syria.
The Syrian Observatory for Human Rights, a monitoring body based in Britain, reported heavy bombardment by government forces in the area, including the town of Kafr Zita and other towns on Sunday.
The Observatory said helicopters had dropped "barrel bombs" made from oil drums near the hospital the day before, and cited sources as saying they caused several people to choke - a sign of a gas attack. Rebels also said there had been a chlorine attack in the area.
The government vehemently denies using chemical weapons, but a United Nations inquiry last month said the Syrian military had been responsible for poison gas attacks in the past.
"The chlorine attack the night before had 30 victims, most of whom were treated at the cave," said Adham Sahloul, an advocacy officer at the Syrian American Medical Society, which funds most of the hospital's operating costs. "But they were out of the hospital by then."
Doctors at the hospital perform more than 150 surgeries and treat at least 40 intensive care cases from rural areas near Hama every month, according to UOSSM.
The hospital provides all medical treatment without charge, and mainly serves people living in nearby towns who had already fled their homes in other parts of Syria. Some wounded rebels are also treated there, al-Dbis said.
"I will not hide it, there's great fear among the hospital staff," Darwish, the hospital director, said. "But God willing, we will get back to work after the repairs. And when they stay deep inside the hospital, nothing will happen to them." (Additional reporting by Tom Perry; Editing by Angus McDowall and Peter Graff)