MOSCOW — Drivers in downtown Moscow were squinting in disbelief as an electronic highway billboard blazed a two-minute pornographic video in place of the regular advertising clips.

Late-night traffic on one of the Russian capital’s busiest roads slowed Thursday as a couple’s explicit escapades appeared across the 9-by-6-meter (yard) display.

The screen’s owner – the 3 Stars advertising agency – has told The Associated Press that a hacker attack is likely to blame. City police say they have yet to receive any complaints and have not opened an investigation.

Russian news agency RIA Novosti quoted a city official as saying that Moscow will bolster security of data transmission to ad screens.

Mobile phone camera footage has been posted on popular video-sharing Web sites.