Tbilisi - Twenty people were missing on Monday after devastating floods killed more than a dozen people in Georgia, with escaped zoo animals - including two tigers - still on the loose.The death toll from the worst floods to hit the capital Tbilisi in decades rose to 13 after rescuers found an elderly man in the rubble of a destroyed house, government spokeswoman Manana Tokmajishvili said.As many as 300 zoo animals also perished. Twenty people were missing as of Monday afternoon, Tokmajishvili added, with the death toll expected to rise further.The small Vere River running through the city of 1.2 million burst its banks early Sunday after hours of torrential rain, paralysing Tbilisi and wrecking the city's zoo.Many birds and animals including monkeys and penguins drowned in the muddy waters, but lions, tigers and even a hippopotamus escaped and were either recaptured or shot dead by police.Two tigers, a bear and a jackal were still at large, however.Survivor Bela Gvelesiani, whose house was destroyed by the flood, told AFP that "everything happened in just two minutes."I looked through the window and saw that the river was in my courtyard. I can't remember how we managed to get out. At first the water reached our ankles and in a split second we were up to our necks."Screaming for helpHer elderly neighbour Dusia Tsiklauri added: "My house was completely destroyed, but my thoughts are with my neighbours who died, with those still missing."Another resident Aleko Korkotashvili said, "I saw a man clutching at a lamp pole in the middle of a violent torrent. He was screaming, asking for help, but we were unable to help him." In an emotional show of solidarity after the disaster, hundreds of Tbilisi residents volunteered to join a clean-up operation across the city."What happened was an apocalypse," renowned Georgian actor Giorgi Nakashidze said as he helped National Guard soldiers clear mud and fallen trees from the streets."In my lifetime, I didn't see such a tragedy in our country. All those who care about our city, about people, should help rescuers and those who have suffered," he said in televised remarks.Officials were still trying to hunt down the missing zoo animals on Monday, Tbilisi zoo spokeswoman Mzia Sharashidze told journalists."The search for animals is still underway," she said, adding that some 300 animals had died.Ivane Daraselia, Tbilisi zoo vet told local television that two tigers, a bear, and a jackal were still on the loose as of Monday evening.Some animals including two bear cubs were found kilometres away and returned to their enclosures on Monday.Outpouring of support The disaster left dozens of families without homes, destroyed several roads in central Tbilisi and seriously disrupted traffic.Some homes were swept away along with cars, with the floods even washing coffins out of the ground in a cemetery."It was a disaster on an unprecedented scale," said 23-year-old volunteer Tsotne Japaridze.Georgian Prime Minister Garibashvili praised the "tremendous" contribution of the volunteers."In our own country, we were moved by an unprecedented show of solidarity as volunteers took to the streets to help with the relief effort," he said in a written statement."The solidarity and support which Georgia has received in response to this disaster has been overwhelming."Local residents were also raising money and collecting food and clothes to help the victims.Initially put at $15m, the damage to Tbilisi's infrastructure would "in fact be much higher", Finance Minister Nodar Khaduri told journalists, adding that officials were still counting the costs.Tbilisi Mayor David Narmania said reopening a four-kilometre highway linking the city's two central districts would "take a long time".