Russian politicians, businessmen and journalists demanded an explanation yesterday for the jailing of the owner of Russia's only independent national television, warning of a clampdown on free speech.
President Vladimir Putin, on a visit to Spain, played down suggestions that the arrest was politically motivated and promised to look into the case after his return to Moscow.
Mr Vladimir Gusinsky, whose liberal television, radio, newspaper and magazine group has often criticised the Kremlin, was detained on Tuesday evening on suspicion of embezzlement and held in the overcrowded Butyrskaya jail. He was questioned yesterday and his lawyers said he planned to stand firm against the accusations.
A senior official in the prosecution service, Mr Vladimir Lyseiko, told RTR state television that the case involving Mr Gusinsky (47) had been under investigation for about two years. Mr Lyseiko added that charges against Mr Gusinsky would be brought within 10 days, as required under Russian law. If that did not happen, he would have to be released.
The arrest sent a tremor through Russian financial markets. The so-called oligarchs - business figures like Mr Gusinsky with varying degrees of political influence - wrote a joint letter to the prosecutor's office condemning the arrest.
"Until yesterday we believed we lived in a democratic country and today we have serious doubts," said the letter, whose signatories included Mr Rem Vyakhirev, who heads the gas monopoly Gazprom, Mr Anatoly Chubais, a leading liberal and now head of the national electricity grid, and leading bankers.
Mr Putin, speaking in Madrid on the first leg of a foreign tour which will also take him to Germany and Moldova, said he needed more information about the circumstances of Mr Gusinsky's arrest. "If there is a political aspect to this case I am unaware of it. I am also unaware of the criminal aspect of the problem. I simply know nothing about it," said Mr Putin.
"Once I am back in Moscow I shall get information on all aspects of the case and, naturally, if there have been violations of the law, all those who allowed themselves to break the law will face an appropriate response from the state."
Mr Putin said however that Mr Gusinsky owed large sums of money to creditors, including the state.
At a subsequent joint news conference with the Spanish Prime Minister, Mr Jose Maria Aznar, Mr Putin said he had tried to contact the chief prosecutor, Mr Vladimir Ustinov, about the case but he was away from Moscow on a trip.
Mr Ustinov's office issued a statement criticising some of the media reaction to Mr Gusinsky's detention. "The press has unleashed a mass campaign, in the course of which some journalists have shamelessly distorted facts and, carried away by their emotions, have ignored both legal and professional ethics," the statement said.
At another news conference in Madrid Mr Igor Malashenko, deputy chairman of Mr Gusinsky's Media-Most group, attacked the arrest as "a Kremlin war against the media".
Mr Malashenko had flown to the Spanish capital on Tuesday evening in an attempt to speak to Mr Putin about the case.
In Moscow, traders said the news had hit share prices.
Several politicians and commentators saw in the arrest the hand of Mr Putin's powerful chief of staff, Mr Alexander Voloshin, and other members of a group of senior businessmen and aides close to the former president Mr Boris Yeltsin.
The former Soviet president Mr Mikhail Gorbachev said he believed that "clans" in the Kremlin were working behind Mr Putin's back while he was in Spain, seeking to undermine reforms he has launched.
Leaders of the liberal Yabloko and SPS parties and the centrist Fatherland-All Russia party issued a joint appeal to Mr Putin to clarify the situation.
Moscow's mayor, Mr Yuri Luzhkov, named Mr Voloshin and said that Mr Gusinsky should be freed immediately, offering to take his place in jail if the businessman should then flee the country.