As the opening of the Olympic Games draws closer, the Greek police and foreign intelligence agencies have increased their activities in a predominately Muslim area of Athens, Greek officials say.
Residents of the district - whose narrow streets are lined with open-air shops selling such items as cement, clothes and onions, next to international call centers and places to wire money abroad - say they are incensed that they are being treated as terrorism suspects.
Greek, American and British intelligence agencies have all tried to infiltrate the Muslim and Arab communities here, Greek officials said. But the Greeks asked for, and received, assistance from counterterrorism teams and intelligence operatives from Jordan and Egypt, the officials said. The Israelis have helped keep an eye on Arab embassies, they said.
About 100,000 people of Arab or Muslim background live in Athens, and they have generally not been militant, Greek officials said. But their fear, heightened after the bombings in Madrid in March, is that Al Qaeda or some affiliated terrorist organization has planted a sleeper cell in this part of the city.
"If one were looking for a sleeper cell, this is where it would be," Alex Rondos, a former ambassador at large who was coordinator for Olympic activities, said of the area, near Omonia Square in central Athens. Mr. Rondos, who left office in March when the Socialist government was defeated, said his concerns arose more than a year ago, when he was working on various counterterrorism projects. The possibility of a sleeper cell, however remote, is something that Greek officials were slow to grapple with, he said.
"There was a dangerous attitude of complacency," he said.
Fears of a possible attack by Islamic militants are not allayed by the statements made by Mehmet Imam, president of the country's largest Muslim organization.
Mr. Imam has called on all Islamic countries to boycott the Games, because of the fighting in the West Bank and Gaza, Afghanistan and Iraq. "He is an enemy," Mr. Imam said in an interview, about anyone who attends the Games. But he disavowed any link to Al Qaeda or any sympathy for Osama bin Laden.
He said the Greek police were using the Olympic Games as a pretext to oppress Muslims.
Terrorism investigators in Europe have found cells in many countries, including France, the Netherlands, Germany, Italy and, most recently, Spain. But they have not found any trails leading to Greece, Greek and other European officials say.
The Greek government has discovered that monitoring possible suspicious activity within the largely Muslim part of the city has been made more difficult by one of its own policies. In spite of repeated promises, the Ministry of Religious Affairs has not given the necessary approval for a mosque in Athens, because of the opposition of the Greek Orthodox Church, the official state religion.
"It is not a culturally sound policy, and it is counterproductive from a counterterrorism view," Mr. Rondos said. Instead of one central mosque, where the authorities could watch for suspicious people and listen for incendiary sermons, there are about 50 "underground" mosques, in tenement apartments and garages, Greek officials said.
Ahmed Asak, a 32-year-old garment worker from Bangladesh, said that he was stopped by the police 10 days ago in this district. They wanted to check his documents, to be sure he was in the country legally, and they looked in his backpack.
The same thing happened to Thomi Savr, 28, who managed to get out of Iraq three years ago. He made it to Greece via Turkey, was jailed for three months, then went to Germany, where he married. Then the Germans sent him back to Greece.
Mr. Asak goes to Friday Prayers on the second floor of a rundown eight-story tenement on Geraniou Street, within a few blocks of City Hall. Nigerians and Somalis live on the first floor, Bangladeshis on the third, Sudanese on the fifth, Afghans on the eighth.
At another tenement mosque, attended by Pakistanis, speakers have extolled the virtues of Osama bin Laden, a Western ambassador in Athens contended. He said he had been told this by a Muslim on his staff.
Saudi Arabia has been sending money to various Muslim groups in Athens, Greek officials said, and the Greek government has spoken to the Saudi Embassy about it.
In trying to stop any potential terrorist from disrupting the Games, the Greek government has had some important help beyond all the high-tech gear and spies sent by the United States, Britain and other countries.
Col. Muammar el-Qaddafi of Libya has sent word to the Libyan population in Athens that its members should not engage in any acts of violence during the Games, a Greek official said. The Palestinians have made a similar appeal to their residents here, who number about 25,000, he said.
The Turkish government has promised Greece that it would crack down on the smuggling operations that bring refugees through Turkey en route to Europe. The smugglers' routes go through Greek waters, and there is a concern that a potential terrorist could reach one of Greece's many islands.
The men on Geraniou Street reacted strongly to Mr. Imam's call for a boycott, though they tended to agree with his view that the police were using the Games as a pretext to harass them.
"Muslims love sports," one man said, his voice rising above those of the others in the crowd on the second floor.
"The Prophet says we should be good at sports," another said.