The US ambassador to Moscow questioned Friday how a Kremlin-linked television channel accessed his private schedule, calling Russia a "wild country" in an altercation with its reporters.
Michael McFaul wrote on Twitter that NTV, a state-run broadcaster that has aired smear documentaries against the opposition, seemed to know his appointments and was waiting as he came to visit a prominent rights activist.
"Not true. State Dept does not publish my schedule," McFaul said on Twitter, adding that the meeting with activist Lev Ponomaryov from the For Human Rights group had not been scheduled through the consulate either.
NTV published a statement on its website saying the channel had a "wide network of informants."
The Russian media has given McFaul a rough ride since he took up his post in January, during mass protests against Vladimir Putin's return to the Kremlin.
He was slammed for meeting opposition leaders on his second day at work.
A commentator on state-controlled Channel One even speculated whether the author of a book called "Russia's Unfinished Revolution" had come "to finish the revolution."
McFaul is far from the first diplomat in Moscow to complain of harassment in recent years.
In 2006, pro-Kremlin groups picketed the British embassy, accusing then-ambassador Tony Brenton of financing the opposition and calling for him to resign.
In 2007, the Estonian ambassador Marina Kaljurand suspended the embassy's work after pro-Kremlin activists tried to physically attack her in protest at a Soviet war memorial being moved from central Tallinn.
McFaul, a former academic specialising in politics, was one of the architects of US President Barack Obama's "reset" in relations with Russia. He is the first US ambassador in Russia to constantly air his views on Twitter.
In a meeting on Friday, the influential head of the Russian Orthodox Church, Patriarch Kirill, urged McFaul to help heal what he acknowledged as a rift between the countries.
"I'm convinced there can be no reset until we change our attitudes toward each other," the patriarch said, quoted by Interfax news agency.
"Of course we can rub salt on the wound and create negative attitudes toward each other, but this is counterproductive."
NTV late Thursday aired a video of McFaul, a fluent Russian speaker, grilling its reporters on how they knew of his meeting and accusing them of hounding him.
"How did you know about this meeting, if that's not a secret? How did you get the information that I would be here? You can't answer," he said.
"For me this is a very serious question because this is against the Geneva convention if you are going to get information from my telephone or my Blackberry," McFaul said.
In the footage, a woman reporter seen on camera told him she heard of the meeting from "open sources" without specifying.
Visibly riled, McFaul told the journalists their behaviour reflected badly on Russia.
"This is a wild country, it turns out. This is not normal. It does not happen in our country, it does not happen in Britain, in Germany, in China. Only here and only with you," he said.
He later apologised for the comment on Twitter, explaining he meant to say the NTV crew was acting wildly, not that Russia was wild.
US State Department spokesman Mark Toner told a press briefing Thursday that McFaul had wondered how media was "getting word about his schedule," but did not comment on the possible involvement of the Russian government.
"I'll just say he was asking a rhetorical question," Toner said.
Shortly before he ended his term in Russia in 2008, Britain's Brenton told The Mail on Sunday weekly that: "One of the sad things about working here is that you have to assume you are being listened to."