Chinese policeman (L) takes pictures of crime site on Drum Tower in Beijing, 09 Aug 2008

The first full day of competition in the Beijing Olympics was marred by a fatal stabbing attack on American tourists, several protests and questions about a dissident's missing family.

Chinese officials said a man from southeastern China stabbed two Americans and their Chinese tour guide on Saturday before the attacker leaped to his death from Beijing's Drum Tower.

One of the Americans, Todd Bachman, the father of a former Olympian and father-in-law of the U.S. volleyball coach was killed in the attack. His wife and the tour guide were hospitalized.

The international police agency Interpol said the attacker appeared to have no ties to terrorism groups, but the investigation was continuing.

China has assigned more than 100-thousand police and soldiers for Olympic security.

Also Saturday, the group Chinese Human Rights Defenders says the wife and infant child of jailed dissident Hu Jia have disappeared and may have been detained by authorities. The group says it has had no contact from Zeng Jinyan since August seventh -- the day before the Olympics opened.

And a Tibetan rights group says five of its members -- three Americans, a German and a Canadian -- protested in Beijing's Tiananmen Square on Saturday and were detained by authorities.