Watch the fake report on Imedi TV
Russia has condemned as "irresponsible and immoral" a Georgian TV hoax about a Russian invasion.
Panic was sparked in Georgia after the Imedi TV station broadcast news that Russian tanks had invaded the capital and the country's president was dead.
The broadcast rekindled memories of the 2008 war between Russia and Georgia.
Russia's foreign ministry said Georgian President Mikheil Saakashvili approved of the hoax. The ministry accused Tbilisi of "political paranoia".
Georgia's mobile phone networks were overwhelmed with calls on Saturday, and many people rushed onto the streets.
Pro-government Imedi TV said the aim had been to show how events might unfold if the president were killed. It later apologised.
The head of the holding company which owns Imedi TV, George Arveladze, said he was sorry for the distress that the TV report had caused.
For a brief moment on Saturday evening many Georgians thought history was repeating itself, the BBC's Tom Esslemont in Tbilisi says.
1926: Mass anxiety after a BBC report of a murderous riot in London - it was a spoof by a literary priest
1938: Thousands flee after a CBS Radio report on Martians landing in New Jersey - it was a radio version of HG Wells War of the Worlds
1994: Panic in Taiyuan, China, after a TV report of a deadly creature on the loose - it was a commercial for a new brand of liquor
It is only 18 months since Russian tanks came within 45km (28 miles) of the Georgian capital, our correspondent adds.
In its news report, Imedi TV showed archive footage of the war and imagined how opposition figures might seize power after an assassination of President Saakashvili.
Although the broadcast was introduced as a simulation of possible events, the warning was lost on many Georgians, our correspondent says.
One local news agency reported that emergency services had received an unusually high volume of calls in the ensuing minutes.
And once calm returned, the report was seen by some as a poorly disguised swipe at the Georgian opposition politicians who recently travelled to Moscow to meet Russian Prime Minister Vladimir Putin.
Mr Arveladze told Reuters news agency that the aim was to show "the real threat" of how events might unfold.
That did not stop dozens of journalists and angry Georgians who gathered outside the Imedi TV studios to protest.
One opposition politician who was there labelled the report "disgusting".