A local court sanctioned the arrest on the grounds that Dymovsky had put pressure on an investigator, local human rights campaigner Vadim Karastelyov said.

"During the hearing it turned out that he had supposedly threatened a law enforcement officer taking part in the criminal investigation," Karastelyov told Interfax.

Dymovsky was dismissed from the police force after posting two online addresses last November in which he complained to Prime Minister Putin about rampant corruption in the police force. Last week, he was charged with fraud and abuse of office, and he faces up to six years in prison if convicted.

Karastelyov said Sunday that authorities refused to immediately hand over warm clothes brought to Dymovsky. "Today his lawyer brought clothes to the pretrial detention center, but according to their rules he will receive them only on Monday, Karastelyov told Ekho Moskvy radio. Temperatures in the Black Sea port stood at minus 8 degrees Celsius over the weekend, according to the Meteonovosti.ru web site.

In an audio recording taped just before Friday's hearing, Dymovsky accused investigators of fabricating the reason for his arrest. In the message, posted on his web site, Dymovskiy.name, he explained that investigators unexpectedly told him Thursday that he should appear for a court hearing that would consider his arrest the next day. "They told me they had evidence I had put pressure on members of the investigation and witnesses," he said.

"I believe that I will be detained today — this is a political case that was ordered," he said.

Human rights campaigners voiced anger about the arrest. "A man speaks out about his superiors' illegal actions. ... Now he is arrested. This is outrageous," said Lyudmila Alexeyeva, head of the Moscow Helsinki Committee, Interfax reported.