Five people, including a mother and her two children, were killed when flooding brought by heavy rains destroyed houses overnight in the Georgian capital Tbilisi, officials said on Sunday.

The rains sent torrents of muddy water through the city's rundown Ortachala district where many people live in dilapidated housing.

Local television showed buildings partially collapsed or submerged and cars overturned by the flood amid streets strewn with debris, as emergency services workers lifted residents to safety.

Georgian media reported that resident Ana Tskrialashvili and her two children aged five and six months were killed after being trapped in a small house when it was hit by flood waters.

Local resident Nino Chikvadze told Georgian television: "Everyone in the district lost something, there was water in every house."

"The water was washing everything away, even cars," said another resident, Medea Bregvadze.

The ex-Soviet state's President Mikheil Saakashvili sent his condolences to families of those who died.

"The president of Georgia expresses deep sorrow over the tragedy that occurred as a result of this disaster," he said in a statement.

The Georgian leader later visited the affected area to observe the clean-up operation and meet relatives of the victims.

He called for a long-term project to improve conditions for people living in the substandard accommodation typical in poorer parts of Tbilisi, saying, "We should do everything to prevent people from living in such slums."

Officials said it was not yet possible to estimate the cost of the damage and that the clean-up operation could take several days.

"We will be working through the night if that is necessary," Tbilisi's emergency situations chief Temur Giorgadze told local television.

Flooding also caused serious damage to property and farms in rural regions all across the impoverished Caucasus country, local media reports said.