Bulgarian seismologists have called for patience and calm after a 3.5 magnitude earthquake shook the capital Sofia on Friday, throwing many people into panic.

"We, seismologists, hope that the quakes that hit Sofia for the last two weeks are part of a series of weak tremors, which is a sign that the earthquake is dying down and coming to an end," Nikolay Miloshev, director of the National Geophysics and Geography Institute, told Darik radio.

The expert specified that the other pessimistic scenario is for the serious of tremors to culminate in a stronger earthquake.

"Both scenarios are possible, we can't say which is more likely," he added.

According to the Richter scale, earthquakes with a magnitude of 3.5 or less are generally not felt, but that was not the case here due to the shallow and close epicenter.

"This does not mean that this kind of earthquakes are not dangerous and scary to the people, but they don't lead to damages or casualties. The only damages they bring are those inflicted on the nerves of the people. And today people got really scared - they are calling me all the time, asking me what to do," Miloshev said.

The 3.5 earthquake that shook Sofia on Friday caused the falling of four chimneys in the Bulgarian capital and interrupted mobile phone traffic.

The National Seismology Institute announced that the earthquakes that shook Sofia on Friday were two. They measured 3.5 and 3.3 on the Richter scale and both had their epicenters in Sofia.

Rumors of an explosion, this time said to be located in the subway, once again surfaced as during the previous tremor last week, but those were quickly dispelled.

Some residents, living or working in the suburban districts, described the sound from the quake as similar to thunder.

"We heard this loud bang and my entire desk shook," they said.

The tremor was reported to have been felt strongest in downtown Sofia.

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