VIENNA - The United Nations nuclear watchdog is training Chinese security personnel to respond to any radiological attack during the Olympic Games in Beijing in August, officials said on Friday.

A radiological attack is one involving a release of radioactivity -- for example through a "dirty bomb" in which radioactive material is packed around conventional explosives and scattered when the device goes off.

The watchdog, the International Atomic Energy Agency, has provided similar assistance at previous sporting events including the 2004 Athens Olympics and the 2006 soccer World Cup in Germany.

"The awareness after the 9/11 attacks (was) that there are basically no limits for what can be done," said Anita Nilsson, director of the IAEA's Office of Nuclear Security.

"In this case it is better to be proactive, to review the practices and to put them up to standard and to implement them," she told journalists.

The training and preparation in China were about adding a dimension to standard security systems in order "not to leave any stone unturned, to have the best possible Olympic Games or championships, not to be disturbed by these undue events."

Nilsson said there was no specific intelligence pointing to a threat to the Olympic Games taking place in Beijing from August 8-24.

IAEA security expert Peter Colgan said two field exercises had been taking place this week in China.

One of them simulated an attempt to smuggle a radioactive source into a venue, and was aimed at testing detection capabilities as well as the response and communication between security personnel. The other involved a suspect package being found in a restaurant.

"I understand the exercises went very well," Colgan said.