Athens, Greece ? Greece asked NATO on Friday to help safeguard the Olympics after the deadly train bombings in Madrid heightened worldwide concern about safety at major sports events.

Bomb squads and dogs joined expanded patrols at train stations across Greece as part of boosted security measures leading to the Aug. 13-29 games.

Greece’s request to NATO came a day after Spain’s worst terrorist attack. Ten bombs blew up four trains during morning rush hour and killed nearly 200 people. Spain blamed Basque separatists, but a group claimed responsibility in the name of al-Qaida.

NATO was asked to provide aerial and sea surveillance against a “chemical, biological and nuclear incident.” Athens’ massive security preparations already cost a record $800 million and involve 50,000 police and troops.

“This is part of a general effort for international assistance and participation … to deal with consequences (of attacks) that exceed the capabilities of our country,” police spokesman Col. Lefteris Ikonomou told The Associated Press.

NATO said even before the attacks that it was willing to help. A seven-nation advisory group — Australia, Britain, France, Germany, Israel, Spain and the United States — is assisting Athens with security training and planning.

U.S. and Greek forces are taking part in a major security drill in Athens and other Greek cities holding Olympic events.

The Madrid bombings prompted security alerts at transportation points and other potential terrorist targets in several countries.

Authorities in Portugal, which is preparing for the Euro 2004 soccer championships, said security concerns shifted overnight from rowdy fans to potential terrorist threats. Officials are considering whether to install metal detectors at stadium gates for the June 12-July 4 tournament.

“These bombings make us feel that the world is more insecure. We must ensure security is handled in the best possible way,” said Leonel Carvalho, the Euro 2004 security coordinator. “We need to exchange information at all times and combat any terrorist threats.”

In Karachi, unprecedented security was ordered Friday as India’s cricket team arrived for a one-day international in its first full tour of Pakistan in 14 years.

About 500 police commandos escorted team members to their hotel, while more than 5,000 police and 1,500 paramilitary officers were deployed in and around the city’s National Stadium.

It was not clear whether the Madrid attacks had a direct impact on the security, already tight because of the history of bitter relations between the two neighbors.

The bombings brought signs of sympathy across the sports world.

The German soccer club Bayern Munich offered to play a charity game with Real Madrid to raise money for the survivors and relatives of the victims. Spanish cyclist Oscar Freire wore a black armband as he took the overall lead in Italy’s Tirreno-Adriatico race.

Spanish golfer Miguel Angel Jimenez, playing at the Qatar Masters, said he was stunned by the bombings.

“I have seen the TV pictures and got to see what happened in Madrid,” he said. “It is very sad. I have lots of friends all over Spain and I was concerned. All of a sudden, golf is not that important now.”