St. Petersburg residents were scratching their heads about the existence of UFOs on Tuesday after seeing mysterious lights hover over their city overnight.

At least four people in the north of the city captured the unidentified lights on video on Monday night and posted them to YouTube.

"I filmed this out of the window in the evening," wrote one person, who identified himself only as Newnarva. "There were two objects. After I ran for my camera, only one was left."

The 27-second video, titled "UFO or What Is It?", shows four bright lights hovering in the pale evening sky to the side of a tall building before disappearing behind it.

One viewer wrote under the video that he also had seen the lights but had not managed to film them.

Similar videos of unidentified lights were uploaded by YouTube users stepacademymail, monplezirvideo and Marina Muskina. Voices can be heard in the videos trying to make sense of the lights.

The BaltInfo news agency said the whole city was discussing the sightings and that its offices had received phone calls from worried residents.

"My daughter who lives over on Grazhdanke told me about a UFO," one caller said. "I live on Komendantsky Prospekt. I looked out the window and also clearly saw an orange spot. Then one spot separated and plummeted downward. The spot flickered, disappeared and reappeared. It is visible in various neighborhoods."

At least one Leningrad region resident also claimed to have seen a UFO on Monday night. The person, ckvizecrew, wrote that the lights appeared over the Leningrad region around 6 and 7 p.m. and, after hovering for a while, sank toward the Earth for a possible landing.

Little can be seen in the 13-minute video other than bright orange points of light floating in pitch blackness. Male and female voices can be heard excitedly talking about what they are seeing.

While the authorities have not weighed in on the sightings, a St. Petersburg scientist said last month that aliens probably keep their distance from humans.

"Aliens look at us as if we are idiots, undeveloped people," said Sergei Smirnov of the prestigious Pulkovo Observatory outside St. Petersburg. "Perhaps they have fenced us in with their own sort of screen for the whole galaxy and are sending warnings to hundreds of billions of stars that the civilization near the Dwarf star, which we call the Sun, is dangerous."