MOSCOW - An enormous television screen showing a pornographic film caused a midnight traffic jam in central Moscow Thursday as stunned motorists slammed on the brakes to gawk at the writhing naked bodies.

The owner of the advertising screen, which sits atop a main road about two km (1.2 miles) south of the Kremlin, told the state-run RIA news agency that hackers had broken into the screen's computer system and turned on the porn.

"They were either acting out of hooliganism or were from a rival company," Viktor Laptev, commercial director of advertising firm Panno.ru, told RIA.

A short clip showing cars slowing to a halt to look at the screen sprung up on youtube.com and internet sites Friday across Russia, a country which banned nudity on television before the Soviet Union fell in 1991.

Authorities said they are investigating, RIA added.