President Bush praised China's leadership today for its swift response to a deadly stabbing that killed the father of a former American Olympian and left his wife seriously wounded.

Chinese officials said security around the Olympic venues was already sufficient but they would step up protection at the city's many ancient monuments that attract thousands of local and foreign visitors each day. Wang Wei, vice president of the Beijing Olympic organising committee, said the rare attack on a foreigner was an isolated incident. "Beijing is a safe city, but unfortunately we are not immune to violent acts," he said.

Meeting his Chinese counterpart, Hu Jintao, this morning, President Bush voiced his appreciation for the rapid response of the Chinese police to the murder-suicide that marred the first day of the Beijing games.

Todd Bachman and his wife Barbara, parents of 2004 volleyball Olympian, Elisabeth Bachman, were assaulted as they strolled around the upper storey of the 13th century Drum Tower in the heart of the capital yesterday. Todd Bachman was walking a few steps behind his wife and daughter when he was stabbed by a stranger. His wife turned to help and was in turn attacked.

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Dale Bachman, a cousin, said "That's when she was attacked. To me, that was strong indication of her love. She is a fabulous person."

Barbara Bachman was fighting for her life in a Beijing hospital today after undergoing eight hours of surgery for multiple wounds and lacerations. Her husband was pronounced dead at the spot. Their Chinese tour guide was also attacked, but suffered less serious injuries.

Their attacker, 47-year-old unemployed Tang Yongming from southeastern Zhejiang province, leapt to his death from the 130-foot balcony of the tower where, during imperial days, beating of the drums would ring out the hours across the city.

Yang Fengye was working in a small cafe next to the popular tourist site when she heard a scream. "I rushed out and lots of people were running into the Drum Tower. A man had jumped and his body was lying on the stones. There was lots of blood. It was horrible. We thought there must have been some kind of fight," she said.

She said ambulances arrived swiftly at the scene, followed by helmeted riot police armed with machine guns who cordoned off the area for several hours. The Drum Tower was closed today. A few curious onlookers who had heard the news stopped to peer through the locked gates to try to get a glimpse of the scene of the rare tragic drama.

Attacks on foreigners in tightly controlled China are extremely rare and officials could give no motive for Mr Tang's savage assault on the American. Mr and Mrs Bachman are parents-in-law of U.S. men's volleyball coach Hugh McCutcheon.

Beijing organisers said the authorities would step up security around tourist sites in the city after Mr Bachman's murder. Wei Wang, Bocog vice-president, reassured Olympic visitors that security was sufficient around the sports venues and insisted that the fatal stabbing was"An isolated criminal act."

No special security has been given to the US Olympic team, which the authorities said was not under threat. "There was nothing on the victim to identify him as an American so there is no reason to think that the act was targeted at Americans," Mr Wang said. "Beijing is a safe city and we believe our security measures are sufficient. On one hand, we want to take safety measures because we are living in a world where surprises happen but we don't want to have any negative impact on access to venues."

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