A car bomb exploded Tuesday outside a police station in Georgia, killing three policemen and injuring 13 other people, authorities said.

The blast occurred near a regional police headquarters in the town of Gori, the closest regional center to the breakaway region of South Ossetia (search), shattering windows of the three-story building and leaving a crater in the street outside.

Of the 13 injured, three were hurt severely, Defense Minister Irakly Okruashvili (search) said in televised comments from Gori, about 60 miles west of the capital, Tbilisi.

The explosion charred several other nearby cars, broke windows, damaged the facade of the police building and left a crater about 10 feet wide in the street.

"This was not a random occurrence," Okruashvili said. "We are dealing with a well- organized terrorist act."

Interior Ministry spokesman Guram Donadze also called the blast a terrorist act, but there was no immediate claim of responsibility, and neither he nor the military chief speculated on who might have committed it.

Okruashvili said authorities were searching for people who were identified as suspects, but he did not say who they were.

Gori is the capital of Georgia's Shida Kartli (search) region, which is adjacent to South Ossetia — one of two separatist regions that have run their own affairs since wars with Georgia's central government in the early 1990s.

Constant tension between South Ossetia and the central government flared into deadly violence last summer, with frequent clashes between police and separatists.

In 2003, three people were injured in an explosion near a theater in Gori, which also is known as the birthplace of former Soviet dictator Josef Stalin (search).

South Ossetians, many of whom hold Russian passports, seek to unite with their ethnic brethren in North Ossetia (search), across the border in Russia.

Since his election in January 2004 as president of Georgia, Mikhail Saakashvili (search) has vowed to reunite the Caucasus Mountains nation by bringing the breakaway regions back into the fold.

Georgia has also been plagued by violent crime, often linked with its large shadow economy, since the Soviet collapse of 1991.

Moscow says Georgia also is a transit route for foreign mercenaries and extremist funds earmarked for rebels fighting Kremlin forces in Russia's breakaway region of Chechnya (search), which borders Georgia.

The police headquarters houses a jail, and relatives of its inmates were demanding to be allowed inside to make sure they were unharmed. Russia's Interfax news agency, citing an unidentified ministry source, said five people were killed — apparently three police and two bystanders.