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

The rains caused torrents of muddy water to sweep through the rundown Ortachala district of the city, causing widespread damage.

Georgian television pictures showed buildings partially collapsed or submerged and cars overturned by the flood, while emergency services workers lifted residents trapped by water to safety.

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

"The President of Georgia expresses deep sorrow over the tragedy that occurred as a result of this disaster," Saakashvili said in a statement on his website.

A clean-up operation was launched early Sunday but officials said it was not yet possible to estimate the cost of the damage cased by the flooding.