In this combination of images from amateur video, customers, some still carrying their drinks, press toward the exit of the nightclub as it begins to fill with fire and smoke. Within seconds the smoke obscures the camera. (Ural-Inform TV/Associated Press)Officials now say 109 people are dead after onstage pyrotechnics ignited the ceiling of a nightclub in the Russian city of Perm.

Patrons struggled to escape through a single exit early Saturday as the blaze tore through the Lame Horse nightclub, witnesses say.

Flames quickly spread along the ceiling, which was covered in twigs and plastic sheeting.

More than 130 people were injured, 90 of them seriously. Many of those are connected to artificial lung ventilators, according to Russian Health Minister Tatyana Golikova.

Authorities say they have arrested the registered owner of the club and a manager and were looking for another four suspects.

President Dmitry Medvedev on Saturday demanded that those responsible for conditions leading to the fire be "punished with the full force of the law.

"They have neither brains, nor conscience," Medvedev said. He declared a national day of mourning on Monday.

Russian officials say club managers had ignored repeated demands from authorities to change the interior to comply with fire safety standards.

Enforcement of fire safety standards is notoriously lax in Russia and there have been several catastrophic blazes at drug-treatment facilities, nursing homes, apartment buildings and nightclubs in recent years.

Russia records up to 18,000 fire deaths a year, several times the per-capita rate in the United States and other Western countries. Nightclub fires have killed thousands of people worldwide.

Perm is a city in the Ural Mountains, about 1,200 kilometres east of Moscow.

With files from The Associated Press