Syrians closed their businesses and kept children home from school Monday in a general strike, a powerful show of civil disobedience to pressure President Bashar al-Assad to end his nearly nine-month-old crackdown on a popular uprising.

The open-ended strike is designed to erode Assad’s main base of support — the merchant classes that have benefited in recent years as the president opened up the economy.

If the economy continues to collapse, Assad could find himself with few allies inside the country, where calls are growing for him to step down. The authoritarian president is also struggling with international isolation and sanctions.

It is difficult to gauge the strength of the strike because the regime has banned most foreign journalists and prevented local reporters from moving freely. But there were signs that it was being widely observed, in particular in centers of anti-government rallies: the southern province of Daraa, the suburbs of the capital, Damascus, the northwestern region of Idlib and the restive city of Homs.

The opposition wants the strike to continue until the regime pulls the army out of cities and releases thousands of detainees.

“Only bakeries, pharmacies and some vegetable shops are open,” said a resident of Homs who spoke on the condition of anonymity for fear of reprisals. He said those stores didn’t close because they sell essential goods.

Security was tight, he said, with agents deployed at every intersection in the city. Gunfire erupted sporadically.

“There is a terrifying security deployment in Homs,” he said.

An official with the United Nations said Monday that more than 5,000 people have died in the uprising. Navi Pillay, the U.N. high commissioner for human rights, told reporters that she had informed Security Council members of the sharp increase in deaths. The United Nations had previously estimated the death toll at 4,000.

Activists said a new round of clashes between Syrian troops and army defectors began Sunday and spread Monday. The violence is raising fears of civil war.

The British-based Syrian Observatory for Human Rights said that fresh clashes between soldiers and defectors were reported Monday in Idlib and that fighting continued for a second day in Daraa.

At least 16 people were reported killed nationwide Monday, most of them in Homs, according to activist networks.

— Associated Press