Police have detained three men suspected of involvement in Thursday's terrorist attack in the southern Russian city of Vladikavkaz, Russia's top security official said.

At least 17 people were killed a suicide car bombing in Vladikavkaz, the capital of North Ossetia. The republic's health ministry reported that 138 people were injured, with 110 still in hospitals.

Federal Security Service head Alexander Bortnikov, who arrived in Vladikavkaz earlier on Thursday to oversee the investigation into the attack, said the terrorists would be punished.

The Kremlin's special envoy to the North Caucasus, Alexander Khloponin, told RIA Novosti earlier in the day that police had "leads going to people involved in this incident."

The blast occurred near the city's central market around 11 a.m. The bomber was identified as a man named Archiyev, and the owner of the Volga car used in the attack was quickly detained.

President Dmitry Medvedev condemned the bombing, saying no effort would be spared to track down and destroy the culprits.

The United States, France and Georgia expressed their condolences over the terrorist attack, while the authorities in North Ossetia declared Friday a day of mourning for the victims.

Relatives of those killed in the incident will receive 1 million rubles ($33,000) in compensation, while those injured will receive between 200,000 rubles ($6,500) and 400,000 rubles ($13,000), the government said.

The bombing is the latest in a series of terrorist attacks that have rocked the troubled North Caucasus in recent weeks, including a suicide attack on a military camp in Dagestan, while the Vladikavkaz market has been the target of terrorist attacks in the past.

In 1999, an explosion killed 55 people and injured 300 others. In 2008, 12 people were killed and over 40 injured in a bus bombing.

Terrorist attacks are common in Russia's North Caucasus republics, including Dagestan and Chechnya, but most target security forces or officials. The Russian government has vowed to clamp down on militant groups while stepping up efforts to boost the local economies.

VLADIKAVKAZ, September 9 (RIA Novosti)