Two US fast-food restaurants in Xi'an, capital of Northwest China's Shaanxi Province, have been rocked by bomb scares in the past two days.

The incidents have resurrected memories of a still unsolved bombing in another of the city's chain stores in 2001.

In this week's scares, a home-made bomb went off in a McDonald's fast-food restaurant in downtown Xi'an on Sunday, causing slight damage but no injuries.

Police said the small bomb exploded in the bathroom of the McDonald's restaurant in Gulou community in the city at 3:30 pm on Sunday.

Preliminary investigations suggest the blast was deliberate, they said.

Police also evacuated a Kentucky Fried Chicken restaurant in a southern suburb of Xi'an and cordoned off the area on Monday morning after restaurant staff reported receiving a bomb threat.

However, no explosive was found and, after an hour's closure, the KFC restaurant reopened its doors, an officer surnamed Jia told China Daily yesterday.

More than 30 officers and a dozen police cars rushed to the restaurant after the bomb threat was reported, he said.

But the prank call seemed to have little impact on the restaurant's trade.

Guo Hua, a teacher with Xi'an Foreign Language University, who eats at the restaurant regularly, said yesterday the chain restaurant still had many customers.

"Investigations into the two cases are still under way," Officer Jia said. "We cannot say whether there is any connection between the two cases."

In late 2001, one person was killed and 28 injured in the ancient city of Xi'an, a former imperial capital near the site of the famed terracotta warriors, when a bomb went off in a fast-food restaurant.

In that incident, a McDonald's restaurant in Xi'an was targeted. Police found a detonator and a timer at the site and said the bombing was well-organized.

Police said an anonymous woman made a phone call to the police 20 hours after the blast at the McDonald's during which she claimed responsibility. She then told police that another blast would soon rock a downtown disco. Police promptly evacuated the disco, but found no explosives.

However, the year-long case is still under investigation and those responsible for the explosion are still at large, police sources said yesterday.