Security forces shot dead the two civilians when they opened fire on a car in the central city of Hama, said the Syrian Observatory for Human Rights.
Elsewhere, fierce gunfights broke out at dawn between forces loyal to President Bashar al-Assad and rebels in the northwestern city of Idlib, the Britain-based Observatory said.
Meanwhile, regime forces resumed shelling of the rebel neighbourhoods of Khaldiyeh and Bayyada in the central city of Homs.
The Observatory said the areas were being targeted by mortars as the army attempted to seize control of the few old districts of the flashpoint city that remain held by rebels.
The security forces now control some 70 percent of Homs, which has seen some of the biggest losses of life of the 13-month uprising in Syria.
On Sunday, regime forces and pro-Assad gunmen killed nine civilians, bringing to 41 the number of people killed since Thursday, the day a UN-backed ceasefire entered into force.
The first batch of international observers tasked with monitoring the truce brokered by the UN-Arab League peace envoy Kofi Annan arrived Sunday in Syria, a UN spokesman said.
The six observers who arrived are the first of 30 monitors who were approved by the UN Security Council in a vote Saturday. The others are expected to arrive in coming days.
(U.H-AK)
Editor: Priyambodo RH
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