The interior ministry of Transnistria, a separatist Moscow-backed territory in Moldova, said Monday that the state security ministry's offices had been hit in what appeared to be a grenade-launcher attack.
No one was injured in the incident, which happened at around 6:00 pm on a public holiday for the Orthodox Easter, the ministry added.
But windows had been blown out in the state security ministry building and "smoke is billowing out of the buildings", the Transnistria region's interior ministry said in a statement.
According to preliminary information, the attackers had used a hand-held anti-tank grenade launcher, the ministry said.
Pervy Pridnestrovsky television channel cited witnesses as saying they had heard several blasts. De-miners, firefighters and paramedics were called to the scene.
Neither the leadership in Transnistria nor the Moldovan government have yet commented on the incident.
Transnistria is an unrecognised Moscow-backed breakaway region that borders western Ukraine.
Moscow still has a military base there as well as a stockpile of some 20,000 tonnes of munitions.
This attack comes after a senior Russian military official last week raised the issue of Russian speakers in Transnistria in the context of Russia's military operation in Ukraine.
Major General Rustam Minnekayev, acting commander of the central military district, on Friday said Russia sought control of southern Ukraine, which could provide access to Transnistria, "where there have been cases of oppression of the Russian-speaking population".
Moldova's foreign ministry summoned Russia's ambassador over the comments, which it called "unfounded and contradicting Russia's position in support of the sovereignty and territorial integrity of our country within internationally recognised borders".