An explosion and gunfire were heard near the main square of Almaty, Kazakhstan's largest city, Reuters correspondents reported from the scene.

Military vehicles were seen moving toward the square, according to Reuters witnesses.

The sound of gunfire came from the direction of the mayor's office, stormed by protesters on Wednesday, at around 5:30 p.m. local time (11:30 a.m. GMT) and again about an hour later.

Dozens of protesters and 12 police died during extraordinarily violent demonstrations in Kazakhstan that saw government buildings stormed and set ablaze, authorities said Thursday. One police officer was found beheaded in escalating unrest that poses a growing challenge to the rule many consider authoritarian in the Central Asian nation.

After breaking into the presidential residence and the mayor's office in the country's largest city Wednesday, demonstrators continued to try to storm more buildings overnight.

"Dozens of attackers were liquidated," police spokesperson Saltanat Azirbek told state news channel Khabar-24, using a term commonly used to describe the killing of people the government labels as terrorists. Twelve police officers were killed in the unrest, according to city officials cited by the channel.

While the president initially seemed to try to mollify the protesters, he later promised harsh measures to quell the unrest, which he blamed on "terrorist bands," and called on the Russia-led Collective Security Treaty Organization (CSTO).

Tens of thousands of people, some reportedly carrying clubs and shields, have taken to the streets in recent days in the worst protests the country has seen since gaining independence from the Soviet Union three decades ago.

Although the demonstrations began over a near-doubling of prices for a type of vehicle fuel, their size and rapid spread suggest they reflect wider discontent in the country that has been under the rule of the same party since independence.