Russia dispatched troops to assist Kazakhstan's security forces in containing a countrywide rebellion on Thursday, as fresh skirmishes between protestors and police forces erupted in the capital Almaty.

Since Wednesday, police in Almaty have claimed shooting scores of rioters. According to authorities, at least 18 members of the security forces were killed, including two who were discovered decapitated. Over 2,000 individuals have been arrested.

According to reports, several people were killed and wounded in repeated clashes in Almaty's main square, alternately controlled by troops and demonstrators on Thursday.

Explosions and gunfire were heard as military trucks, and dozens of soldiers advanced, though the firing ceased shortly after dark.

Military soldiers had already reclaimed control of the main airport from demonstrators.

The landing of Russian troops came in response to Kazakh President Kassym-Jomart Tokayev for assistance from the Collective Security Treaty Organization (CSTO), a military alliance of former Soviet states commanded by Moscow. He attributed the unrest to "foreign-trained terrorists" who seized structures and weapons.

The internet has been disabled throughout the country, making it difficult to determine the scope of the turmoil.

The violence is at its peak in the three decades since Kazakhstan proclaimed independence. Following independence, Nursultan Nazarbayev controlled the country.

Although Mr. Nazarbayev, 81, stepped down as president three years ago, he retained influence through other roles.

Moscow announced the deployment of soldiers for a "counter-terrorist operation" and endorsed Mr. Tokayev's assertion that foreign-trained terrorists are leading the revolt.

According to the Russian RIA news agency, the CSTO's general secretary stated that the overall peacekeeping force would be approximately 2,500 strong and strengthened if necessary.

It was intended to be a quick deployment lasting "a few days or weeks," RIA said.

The US stated that it was closely monitoring reports of the deployment and had concerns about the legitimacy of the forces' invitation to the country.

"We have concerns about that deployment precisely because Kazakhstan, the government of Kazakhstan... has its own resources and the government is, and has historically been, well-fortified," State Department spokesman Ned Price said.

"We will be vigilant for human rights violations and any attempts or actions by foreign forces to seize Kazakh institutions," he stressed.

The rebellion, which began with protests against a New Year's Day increase in fuel prices, became violent on Wednesday when protestors screaming anti-Nazarbayev chants attacked and set fire to public buildings in Almaty and other cities.

Mr. Tokayev responded by sacking his Cabinet, reversing the gasoline price increase, and distancing himself from his predecessor, notably by assuming a solid security position retained by Mr. Nazarbayev.

However, these measures have failed to appease demonstrators.