Lions, tigers and even a hippopotamus escaped from a zoo in the Georgian capital Tbilisi Sunday, adding to chaos caused by severe flooding that killed at least 12 people, officials said.

Police and soldiers were hunting down the animals, recapturing some and shooting others dead, while rescuers airlifted scores of people trapped by the floods.

Prime Minister Irakli Garibashvili warned Tbilisi residents to stay indoors while the zoo animals were still on the loose,

He described the damage to the city's infrastructure as "substantial" after the River Vere burst its banks following hours of torrential rain.

"Our latest estimate is that the death toll is 12," Tbilisi Mayor David Narmania told journalists.

Interior Ministry spokeswoman Nino Giorgobiani told AFP that 24 people were still missing by Sunday evening.

Dozens of families have been left without shelter and thousands more without water and electricity, the mayor's office said.

Several main roads have been wiped out and small houses and cars were swept away by the torrents. In a city cemetery coffins were washed out of the ground.

At the Tbilisi Zoo, spokeswoman Mzia Sharashidze told the InterPressNews agency that three bodies were found on the premises of the zoo, two of them zoo employees.

"The search for animals continues, but a large part of the zoo is simply non-existent. It was turned into a hellish whirlpool," Sharashidze said.

Around 20 wolves, eight lions and a number of tigers, jackals and jaguars had been shot dead by special forces or were missing, she said.

"Only three out of our 17 penguins were saved," she added.

- Hippo in the square -

And on Georgian television, a hippo was shown swimming in the flooded Heroes' Square in downtown Tbilisi as rescuers struggled to capture the animal.

The Tbilisi zoo's director, Zurab Gurielidze, said later that the hippo had been caught and returned to its enclosure.

He also added to the sad toll of how many of the zoo's animals perished in the floods.

"All our lions and tigers are dead. We also failed to save our monkeys. They all drowned, unable to escape their cages," he told Rustavi 2 channel.

The corpses of a lion and a pony lay on the road close to the zoo on Sunday afternoon, an AFP journalist reported.

The government set up a hotline for residents to inform the emergency services if they spotted any of the animals.

- 'I can't stop crying' -

As clean-up operations began, Georgian President Giorgi Margvelashvili visited the affected areas and sent his condolences to the families who lost loved ones in the devastating floods.

"The human losses that we have suffered are very hard to tolerate. I express my condolences to all the people who lost their relatives," Margvelashvili told local television.

Jacob Janjulia, a 21-year-old student who was among the residents volunteering to help the clean-up said parts of Tbilisi were "ravaged".

"It's the duty of all citizens to help rescuers, to help the affected people," he told AFP.

Another Tbilisi resident, 46-year-old dentist Anna Korinteli, wept as she surveyed the scene.

"Such a terrible tragedy, people died, many lost their homes. I can't stop crying," she said. "My heart bleeds when I think of what happened to the animals in Tbilisi zoo."

An interior ministry spokeswoman said rescuers were airlifting scores from flood-affected areas after the heavy rainfall also caused a landslide on a highway outside the capital.

Prime Minister Garibashvili declared Monday a national day of mourning for the flood victims, while the European Commission sent a message of solidarity "with Georgia in this hour of need."

"Our thoughts are with the victims and those who are affected by the deadly floods in Tbilisi," the Commission statement said.

Meanwhile the head of the immensely influential Georgian Orthodox Church, Patriarch Ilia II, blamed the floods on the "sin" of Communists who he said built the zoo using money raised from destroying churches and melting down their bells.

"A terrible tragedy happened, people died in the flood. Tbilisi Zoo is ravaged. When the Communists occupied Georgia, and started repressions against Christians and the clergy and the destruction of churches and monasteries, they ordered church bells to be melted, the metal sold and a zoo to be built with that money," he said in his Sunday morning sermon.

He added the zoo therefore "can't flourish on that place. It must be relocated to a different place. A sin never remains without punishment."

In May 2012, five people were killed in flooding that swept through Tbilisi's ramshackle slums that are home to the city's poo-am/boc