The Britain-based Syrian Observatory for Human Rights said at least 15 people had been killed.
Observatory director Rami Abdel Rahman said the two towns targeted are majority Alawite, the religious community to which President Bashar al-Assad belongs.
Friday's attack came after a double car bombing claimed by Al-Qaeda killed at least 100 people on Tuesday in a majority-Alawite district of the central city of Homs.
The bombings come in a particularly bloody week in the Syrian conflict, which also saw 33 civilians killed in the main northern city of Aleppo on Thursday when government aircraft bombed a popular market in a rebel-held district.
More than 150,000 people have been killed since protests against Assad's rule erupted in March 2011, meeting with repression that sparked an armed rebellion.
Despite the violence, authorities plan to hold a presidential election on June 3, which is expected to return Assad to office.