A Chinese school was shocked to find its website hacked and filled with porno pictures, days after the institution declined to buy advertising services of a country's leading search engine Baidu.com.

Porno pictures popped up when students High School in Feidong County clicked on their school's website prompting the school officials to lodge a police complaint.

The link was fixed yesterday by Anhui's Internet police but not before the students and their parents had been shocked to see pornographic pictures and invitations to download videos on it.

School officials told state run Shanghai Daily that they suspect the hacking might have had something to do with Baidu or its business partners as it happened immediately after they rejected an offer of its promotional advertising services.

Their suspicion were strengthened as they could log into their website without any problem through Google or Sougou but it turned porno when logged through Baidu search engine, which is China's biggest controlling over 70 per cent of the market.

"A middle-aged man tried persuading us to purchase the service that guarantees the top position of the link," School's network director surnamed Zhu said.

"It costs 1,200 yuan for one year but we rejected the offer because the school doesn't need the advertising service."

Both Baidu and its associate company Wangxin Technology Company denied they were involved, when contacted by the Daily saying that some criminals might have been involved in it.

A Baidu customer service official also said it had nothing to do with the incident. It believed the school's system had been hijacked by foreign hackers, as they had found that the server of the attacker was located abroad, he said.

This was not the first time the school's link had been hijacked, Zhu said.

The first attack was on November 7 when some teachers clicked the school's link on Baidu to find they were directed to e-commerce site Taobao.com.

Later, the school's website was turned into an advertising website, with small windows popping up.

Clicking on them downloaded computer viruses.

School authorities said they hadn't ruled out the possibility that some "smart" students were behind the incidents.