Syrian President Bashar al-Assad has exempted thousands of army reservists called up during the civil war from paying debt instalments and late fines during their service, the state news agency SANA said on Wednesday.

The decree was likely meant to boost soldier morale and discourage defections at a time of great strain almost two and half years into a shattering civil war that has seen Islamist-led rebels seize large tracts of Syria.

The law "postpones financial instalments for (reservists) with public banks who joined the military reserve service until the end of the service ... (and all late payment) fines due over the period of service will be exempted," SANA said.

Assad's forces are stretched thin across the country as the opposition has taken further ground. Fleeing reservists say morale is low among troops and that men are virtually imprisoned in their barracks by officers who fear they will defect or flee.

The International Institute for Strategic Studies (IISS) says the Syrian army's strength has been cut roughly in half to around 110,000 men due to a combination of defections, desertions and battlefield losses.

In March 2012, authorities tightened restrictions on men of military age leaving the country to prevent reservists from fleeing.

Since then, Assad has relied on fighters from the Lebanese Shi'ite Muslim militant group Hezbollah and pro-government Syrian militia to back up army operations.

The revolt started in 2011 with peaceful protests demanding democratic reforms from a family-based leadership that has ruled since Assad's father, Hafez, took power in 1970.

Since then, the rebellion has grown into a full-scale civil war with sectarian overtones. Most rebels are drawn from the Sunni Muslim majority, while Assad commands the loyalty of many in his Alawite sect, an offshoot of Shi'ite Islam, and other minorities, who fear retribution if he falls.

According to the United Nations, 100,000 people have been killed in the conflict - by far the bloodiest of the Arab Spring uprisings - and 1.9 million refugees have fled to neighbouring countries such as Turkey and Jordan. – Reuters