The report by the Britain-based Syrian Observatory for Human Rights came as Syria braced for Western military strikes over allegations government forces unleashed deadly chemical attacks last week.
"A car bomb exploded this morning at a military checkpoint in the town of Nabak, on the Homs-Damascus road," killing the nine soldiers, said the Observatory which relies on medics and activists for its information.
After the attack, clashes erupted and the Syrian army bombarded Nabak, it added.
The Observatory also reported army shelling of the town of Ariha in the northwestern province of Idlib, where six women and two children were among 10 people killed.