The Greek police arrested and then quickly released the owner and editor of a respected investigative magazine on Sunday morning hours after he published a list of more than 2,000 Greeks who were said to have accounts at a bank in Switzerland, throwing new controversy into a scandal over whether the government is actively pursuing suspected tax cheats.
The dramatic moves, which were being followed by tens of thousands of Greeks on the Internet, come days before Greece's European partners are to meet to decide whether to grant tens of billions of euros in new aid to the financially struggling nation. Greece's lenders have long said that the government must crack down on tax evasion to be eligible for more aid.
The police said they had been ordered to take the editor, Kostas Vaxevanis, who runs Hot Doc magazine and who is one of the nation's most famous investigative journalists, into custody on misdemeanor charges. The Greek news media reported that the charges concerned the violation of the privacy of those on the list.
Mr. Vaxevanis posted a message to his Twitter account early Sunday saying that 15 officers had surrounded the home of a friend with whom he had been staying "like Greek storm troopers in German uniforms."
Mr. Vaxevanis soon followed up with another Twitter message: "They're entering my house with the prosecutor right now. They are arresting me. Spread the word."
Hours later, he was released from Athens police headquarters to loud cheers from a crowd outside. He is to face a magistrate at noon on Monday, when his trial date is to be set.
On the list were a former culture minister, several employees of the Finance Ministry and a number of business leaders. Hot Doc reported that they had accounts in a Geneva branch of HSBC. The magazine said its list matched a list of 2,059 people that was handed over to the Greek government in 2010 by Christine Lagarde, then the French finance minister and now the head of the International Monetary Fund, to help Greece crack down on rampant tax evasion as it was trying to steady its economy.
A spokesman for Ms. Lagarde referred questions to the French tax authorities, who did not immediately respond to requests for comment.
Last week, as the controversy grew, two former ministers were pressed to explain why the government appeared to have taken no action on the list in the two years since Ms. Lagarde handed it over.
George Papaconstantinou, the ex-finance minister who received the list from Ms. Lagarde, told a parliamentary panel last week that he was advised that he could not use it because the names were obtained illegally by a former HSBC employee. Mr. Papaconstantinou said that after receiving the names, he passed them on a memory stick to the chief of Greece's financial crimes unit, Ioannis Diotis, who later gave it to Mr. Papaconstantinou's successor, Evangelos Venizelos, the current leader of the Socialists. Mr. Diotis said that Mr. Venizelos had not instructed him to investigate it.
Mr. Vaxevanis's publication of the list raises the stakes in a heated battle over which current and former government officials had seen the original — and whether they had used it to check for possible tax evasion.
Moreover, Mr. Vaxevanis' arrest raises questions about freedom of the press in a country that frequently reminds its European Union partners that it is the birthplace of democracy. The Greek chapter of Reporters Sans Frontieres issued a statement on Sunday expressing concern about the speed of his arrest.
"Costas Vaxevanis is not a dangerous criminal," the group said. "The pressure created by the arrest of a reporter is clearly disproportionate. This procedure simply encourages an excessive cover-up, and the authorities appear to be imposing the 'therapy' of this sensitive issue, which is a gripping matter of public interest."
The group added that the handling of Mr. Vaxevanis's case "cannot be any different in a member state of the European Union."
Mr. Vaxevanis said he was the wrong target. "Instead of arresting the tax evaders and the ministers who had the list in their hands, they are trying to arrest the truth and free journalism," he said in a telephone interview that was uploaded on the Internet and widely circulated.
Greek blogs posted petitions calling for Mr. Vaxevanis's release, and they had generated more than 10,000 online signatures by early afternoon.
Greeks are skeptical that political leaders will investigate the business elite, with whom they often have close ties, even as middle- and lower-class people have struggled with higher taxes and increasingly ardent tax collectors. Parliament is expected to vote on a new 13.5 billion euro austerity package (about $17.5 billion) that could further reduce standards of living.
The fallout over the publication of the list is certain to distract Greek politicians, and may raise fresh questions among Greece's European partners during a week when European finance ministers are scheduled to discuss the release of a 31.5 billion euro loan tranche (about $41 billion) that Athens needs to avoid bankruptcy. The magazine was careful to note that having an account at HSBC was not illegal or proof of evading Greek taxes, a point underscored by a spokesman for the Finance Ministry. But the magazine suggested that Greek officials should check whether those on the list had moved money into the accounts to escape paying taxes.
The existence of the list has shaken the country, posing new challenges to the fragile three-way coalition government of Prime Minister Antonis Samaras. There was no immediate comment from Mr. Samaras, who was meeting with aides to discuss the new austerity measures.
Rachel Donadio and Niki Kitsantonis contributed reporting.