An explosion shattered windows Saturday at the headquarters of a party that opposes the forces that brought down former President Eduard Shevardnadze (search), while Georgia's interim president criticized Russia for holding meetings in Moscow with officials from separatist regions in the former Soviet republic.

An explosive device went off outside the Labor party headquarters in downtown Tbilisi (search) before dawn, breaking windows but causing no injuries, police official David Kekua said. Investigators still didn't know what kind of explosive was used.

The Labor party opposed Shevardnadze, who resigned Nov. 23 amid a wave of protests, but it also opposes protest leaders Mikhail Saakashvili, Nino Burdzhanadze and Zurab Zhvania.

"There's no doubt that the junta of Saakashvili, Burdzhanadze and Zhvania have begun a terror (campaign) against our party," Labor leader Shalva Natelashvili told The Associated Press. "They were unable to come to power by constitutional methods ... and now they are trying to scare their opponents."

Later Saturday, local television stations broadcast footage of graffiti in apartment buildings across Tbilisi that read, "Boycott the vote of the junta."

Saakashvili is the favored candidate to replace Shevardnadze in the recently scheduled Jan. 4 presidential election, while Burdzhanadze is interim president and Zhvania has been named state minister, the No. 2 post in the nation in the Caucasus Mountains (search).

The Labor party came in fourth in Georgia's Nov. 2 parliamentary elections, which sparked the protests that led to Shevardnadze's resignation after being widely criticized as fraudulent. Natelashvili had called for the parliament elected Nov. 2 to convene but had not ruled out pronouncing the election results invalid and holding a new vote.

Burdzhanadze has promised new parliamentary elections, but no date has been set. For now, the old legislature elected in 1999 has reconvened.

On Saturday, Burdzhanadze nominated the head of nongovernment organization that conducted independent monitoring of the discredited elections as head of the country's new electoral commission. The nomination of Zurab Chiaberashvili, whose group said that Saakashvili's party received the most votes, was to be considered by parliament Monday.

Also Saturday, Defense Minister David Tevzadze told a news conference he was grateful to military troops and commanders for refusing to become embroiled in the unrest that led to Shevardnadze's ouster and said the military would steer clear of politics.

Meanwhile, tension rose between Georgia's interim leaders and three independent-minded regions as Burdzhanadze criticized Russia for hosting officials from Abkhazia, South Ossetia and Adzharia in Moscow this week.

Burdzhanadze told reporters that "when such meetings take place without notice and completely ignoring the central Georgian authorities, naturally such actions prompt serious irritation in Tbilisi."

Abkhazia and South Ossetia have run their own affairs since seceding from Georgia in the early 1990s, and the leaders of Adzharia have held repeated consultations over the past week with Russia, which has close ties to all three regions.

Abkhazia's Prime Minister Raul Khadzhimba told a news conference in Moscow on Saturday that the region, which broke away from Georgia in a bloody war, is determined to defend its self-proclaimed independence.

"We have existed for 10 years and intend to remain independent," the Interfax news agency quoted Khadzhimba as saying.

Khadzhimba, who met with Russian officials Friday, called for Russian peacekeepers whose presence has angered the Georgian government to remain in the area, but said Abkhazia "has the strength" to defend itself.