Twelve Syrian police wounded in bus blast: state media
The device exploded near Jisr Saida in Daraa province, SANA said.
Daraa province and its capital of the same name, the cradle of Syria's 2011 uprising, returned to government control in 2018.
However, holdout rebels who stayed on in a southern part of the city called Daraa al-Balad continued to battle regime forces last year.
A Moscow-brokered 2021 truce saw dozens of opposition fighters bused out of the city, but some have stayed on.
The Britain-based Syrian Observatory for Human Rights, which has an extensive network of sources inside Syria, said 20 attacks have been recorded in Daraa province since the beginning of the year.
The war monitor says 16 people have been killed in those attacks, including eight civilians.
In October last year, two bombs planted on an army bus in the capital Damascus killed at least 14 people and wounded three others, the worst such attack there in four years, according to SANA.
The Syria conflict, which broke out in 2011, has killed more than half a million people and spurred the largest conflict-induced displacement since World War II.