BEIRUT - Syria sent troop reinforcements Tuesday to two Damascus suburbs that have witnessed anti-government protests as authorities rounded up dozens in the capital, a human rights activist said.

Activists expect protests to escalate during the Muslim holy month of Ramadan, which begins next week. The moves by security forces appear to be an attempt to prevent wide-scale demonstrations when Muslims being the month of fasting from dawn to dusk.

President Bashar Assad's regime has unleashed a brutal crackdown on the four-month-old uprising, and activists say more than 1,600 people have been killed since it began. The government blames the unrest on terrorists and foreign extremists.

Rami Abdul-Rahman of the London-based Syrian Observatory for Human Rights told The Associated Press that hundreds of soldiers and plainclothes policemen were being sent to the capital's suburbs of Zabadani and Moaddamiyeh. He said dozens of people were detained starting late Monday and into Tuesday, including many in the Damascus suburb of Qadam.

Another human rights activist, Syria-based Mustafa Osso said more than 200 were detained in the southern province of Daraa, where the uprising was sparked in mid-March.

On Monday, troops shot dead three civilians in central and northern Syria, Abdul-Rahman said. Among the dead was a woman who was shot when her husband did not stop his car at a checkpoint in the northwestern city of Idlib, he said.

The Local Coordination Committees, which monitors and helps organize anti-government protests in Syria, reported that doctors at a government hospital in Aleppo, Syria's largest city, held a strike Tuesday to protest against the detention of some of their colleagues. The LCC said there are fears that security forces might storm Al-Razi hospital.

The uprising has been the most serious threat to the 40-year ruling dynasty of the Assad family.

Assad, who inherited power in 2000 after the death of his father, President Hafez Assad, has made a series of overtures to try to ease the growing outrage. He lifted the decades-old emergency laws that gave the regime a free hand to arrest people without charge, granted Syrian nationality to thousands of Kurds -- a long-ostracized minority -- and issued several pardons.

The revolt has only grown more defiant in the face of the government response, and protesters have shifted their demands from political change to the outright downfall of the regime.