TBILISI, July 12 (RIA Novosti) - The son of a Georgian opposition leader was admitted to a Tbilisi hospital last night after being injured in a knife attack, the Rustavi-2 TV channel reported on Sunday.

Gaga Gachechiladze, the son of Levan Gachechiladze, a former presidential candidate, was stabbed in the chest by an unknown assailant and taken to hospital in a serious condition. His condition has since improved, the TV channel quoted doctors as saying.

According to preliminary information, Gaga was celebrating his birthday at a restaurant on Saturday evening. He was attacked on the street outside, the report said.

Police are investigating the incident, but have yet to officially comment.

Levan Gachechiladze and other opposition leaders recently announced the creation of a new opposition public movement, Defend Georgia, which aims to bring a peaceful change of power to Georgia.

The opposition is demanding that Georgian President Mikheil Saakashvili resign over his failure to carry out democratic reforms and over last August's disastrous war with Russia.