A China-based cyber attack on Saturday shut down online bookings for a leading Australian film festival, days before a controversial visit by a leading critic of Beijing, organizers said.

The attack on the Melbourne International Film Festival's site is the second in just a few days. It comes after Beijing on Friday summoned Australia's ambassador to protest at Uighur activist Rebiya Kadeer's planned visit to the festival.

Festival spokeswoman Asha Holmes said a site in Chinese had been discovered carrying instructions on how to attack the festival's site. (www.melbournefilmfestival.com.au)

It is definitely China, she said, but added the attack did not appear to be led by the Chinese government but by a group of Chinese citizens.

The festival is to show The 10 Conditions of Love -- a documentary about Kadeer's relationship with activist husband Sidik Rouzi and the effects on her 11 children of her push for more autonomy for China's 10 million mainly Muslim Uighurs, who mostly live in northeastern Xinjiang province.

Kadeer, who lives in exile in the United States, has denied Chinese government claims she organized protests last month which turned into Xinjiang's worst ethnic violence in decades.

On July 5, Uighurs attacked Han Chinese in the regional capital of Urumqi after police tried to break up a protest against fatal attacks on Uighur workers at a factory in south China. Han Chinese in Urumqi launched revenge attacks.

Holmes said that despite the cyber attack, in which fake accounts were used to make massive fake online bookings and show films as sold out when they were not, Kadeer's visa had been granted and her visit would go ahead as planned from Wednesday.

However, it had been a major headache for the festival, Holmes said, as 60 percent of its bookings were normally generated online.

Three Chinese films have been withdrawn from the festival in an apparent boycott.

Ties between Beijing and Canberra have been strained recently by the detention in China of four staff of mining giant Rio Tinto over accusations of commercial spying.

(Editing by Dean Yates)