In an apparent escalation of diplomatic tit for tats, NBC Universal’s film chief Jeff Shell said he was denied entry into Russia and detained by that country’s authorities for about five hours.

Shell was pulled out of the immigration line at an airport in Moscow, while traveling for business late Tuesday night, reports The New York Times. Shell is the chairman of the Broadcasting Board of Governors, the federal agency that oversees Voice of America and Radio Free Europe, government broadcasters that Russia sees as subversive.

“I was then taken to a small room and left alone for about a half-hour before someone came back with a document in Russian that they wanted me to sign,” said Shell, noting that he refused to sign because he couldn’t understand what it said. A translated version of the document stated that Shell had been banned from Russia, but no reasons were given.

Last week, the United States expelled two Russian diplomats in retaliation for harassment that American diplomats have received from Russian authorities. The barring of Shell from Russia appears to be a further escalation.