Syrian authorities sent troops to the country's east on Monday, residents said, a day after a car bomb killed five people in the city of Al Mayadin.
Three police officers were among the dead in the attack, which took place near a security compound in the city, official media reported on Sunday.
The bombing came as a blow to the government's efforts to stabilise Syria, which last week received a boost when US President Donald Trump met Syrian leader Ahmad Al Shara in Riyadh.
Damascus has set up checkpoints near Al Mayadin and other sites along the Euphrates River Valley, where the Defence Ministry is expected to send reinforcements form central Syria, the sources told The National. Ministry officials also visited the site of the bombing.
Local resident Qassem Al Shawa said that the small security presence in Al Mayadinhave made the town an easy target.
Recruitment for new state security forces has been slow in the area, partly as a result of the lengthy screening process aimed at identifying volunteers' past allegiances, he added.
He also noted Al Mayadi's proximity to the Badiya, a vast desert that stretches from the outskirts of Damascus to the Iraqi border, where ISIS fighters are known to operate.
“It is no secret that ISIS has cells in Al Mayadin,” said Mr Al Shawa, who works at Al Omar, a US-controlled oilfield to the east of the city.
On Sunday, an Interior Ministry official told The National that troops had commenced operations to “eradicate” ISIS from urban centres, after a counter-terrorism raid in Aleppo killed three members of the extremist group.
The Syrian government has not yet blamed any group for Sunday's bombing, and there has been no claim or responsibility.
It was the second major attack on a government-held area since the overthrow of former President Bashar Al Assad last year. In February, 20 people were killed in a bomb attack in Manbij, near Aleppo.
Al Omar field and areas to the north of Al Mayadin fall within the domain of the Syrian Democratic Forces, a mostly Kurdish militia that is ideologically at odds with government in Damascus.
