|Muallem, the foreign minister, has warned the US and French ambassadors not to travel outside Damascus [Reuters]
Troops commanded by Syrian President Bashar al-Assad's brother have surrounded the Damascus suburb of Harasta, residents say.
The move appears to be part of an ongoing crackdown on urban centres that have experienced protests on a daily basis.
"Hundreds of Fourth Division troops have sealed off all of Harasta's dozen entrances," a resident of the large suburb, who works as an engineer and managed to leave Harasta, told the Reuters news agency by telephone.
"They are wearing combat fatigues, helmets, ammunition belts and carrying assault rifles. Water, electricity and phones have been cut."
Syrian troops also swept through the central city of Homs, arresting "armed men" and confiscating "stockpiles of weapons", the pro-government Al-Watan newspaper said on Wednesday.
"An uneasy calm has reigned in Homs since Tuesday afternoon after top quality operations by the army, who arrested a number of armed men and seized large quantities of weapons."
Activists say pro-government assailants have killed at least 20 people in Homs since Monday, including seven mourners at a funeral.
Syria's third largest city, Homs has spearheaded demonstrations against al-Assad and his government since protests erupted on March 15.
The army had already entered the city in May in a bid to stop rallies calling for the fall of the regime.
In another development, Walid Muallem, the Syrian foreign minister, cautioned the French and US ambassadors against travelling outside Damascus after they both visited Hama earlier this month.
"We will impose a ban on any [diplomatic] travel more than 25km outside Damascus, if the ambassadors continue to ignore [our] guidance," Muallem said at a meeting broadcast by state television.
"We did not expel the two ambassadors because we had hoped to maintain better relations in future."
Robert Ford and Eric Chevalier, respectively the US and French ambassadors, visited Hama on July 7 amid repeated large demonstrations in the city against Assad.
The Assad government reacted furiously to the visit, accusing the US ambassador of seeking to undermine the stability of Syria and calling in both envoys for consultations.
The Syrian authorities accused the pair of travelling to Hama without authorisation, but the US insisted they had been notified in advance.
The tensions have further intensified since mobs stormed the American and French embassies on July 11.