At least 12 members of Syria's security forces were killed in two suicide car bombings targeting a military intelligence headquarters in the south-central city of Palmyra on Wednesday, a watchdog said.
The Syrian Observatory for Human Rights said that more than 20 troops were also wounded, some in critical condition, after the simultaneous attacks against the intelligence branch and a nearby security building.
It said rebel fighters attacked the buildings soon after the double blasts, while the army deployed security forces in the city renowned for its Roman ruins and which has been designated as a world heritage site by UNESCO.
A shootout around the intelligence buildings erupted after the bombings leaving eight civilians wounded as clashes broke out elsewhere in the central Homs province city.
State news agency SANA reported that "two men blew themselves up in two cars packed with huge quantities of explosives in the residential district of Jamiyeh al-Gharbi" in Palmyra, but did not specify the number of casualties.
Suicide bombings have increased in Syria and are usually claimed by jihadists, the most prominent of them being the Al-Nusra Front, a group designated as a "terrorist organisation" by Washington.
The UN says more than 60,000 people have been killed in violence across Syria since the outbreak of a revolt in March 2011 that morphed into an insurgency after the army launched a brutal crackdown on dissent.
Elsewhere, the Observatory reported fierce battles between the army and rebels in the southern Damascus district of Qadam amid bombardments in the south and east of the capital.
Local residents said that "unusually intense bombing" was heard on Wednesday throughout the capital.
Outside Damascus, troops carried out deadly bombardments on the towns of Irbin, Harasta and Zamalka to the northeast and on Moadamiyat al-Sham to the southwest, where the army is engaged in a protracted battle for control of the area adjacent to the strategic Al-Mazzeh military airport.
Heavy clashes between regime troops and rebels meanwhile broke out in regions across the country, said the watchdog, which gave an initial toll of 41 killed nationwide.
"Syrian army units on Tuesday dealt severe blows to the terrorists (the blanket term for rebels), killing and wounding hundreds of them and destroying their hideouts in the province of Damascus, as well as southern districts of Damascus," pro-government daily Al-Watan reported on Wednesday.
On Tuesday, 106 people -- 42 rebels, 37 civilians and 27 government troops -- were killed nationwide according to the Observatory, which gathers reports from a wide network of activists and medics in civilian and military hospitals.