Syria's state news agency says gunmen belonging to an "armed terrorist group" killed two army colonels in Aleppo, the country's largest city and a strong support base for President Bashar al-Assad.
The officers, identified as Abdel Karim al-Rai and Fuad Shaban, were going to work when they were killed in the city center.
The now year-old revolt against Assad's regime has become increasingly militarized but Aleppo has largely been spared clashes between government forces and rebels.
However, two mysterious bombings in the city this month killed 29 people.
Separately, in the central province of Hama, rebels attacked an army truck and killed two soldiers, activists said.
Fresh clashes between government troops and army defectors were reported also in the country's north and south.
Activists claimed security forces killed at least 11 civilians across Syria on March 29.
Based on reporting by dpa and AP