SYRIAN POLICE LAUNCHED a relentless assault on a neighborhood sheltering anti-government protesters today, fatally shooting at least 15 people in an operation that began before dawn.

At least six were killed in the early morning attack on the al-Omari mosque in the southern agricultural city of Daraa, where protesters have taken to the streets in calls for reforms and political freedoms, witnesses said. An activist in contact with people in Daraa said police shot another three people protesting in its Roman-era city center after dusk. Six more bodies were found later in the day, the activist said.

Inspired by the wave of pro-democracy protests around the region, the uprising in Daraa and at least four nearby villages has become the biggest domestic challenge since the 1970s to the Syrian government, one of the most repressive in the Middle East. Security forces have responded with water cannon, tear gas, rubber bullets and live ammunition. The total death toll now stands at 22.

As the casualties mounted, people from the nearby villages of Inkhil, Jasim, Khirbet Ghazaleh and al-Harrah tried to march on Daraa Wednesday night but security forces opened fire as they approached, the activist said. It was not immediately clear if there were more deaths or injuries.

Democracy activists used social-networking sites to call for massive demonstrations across the country on Friday, a day they dubbed “Dignity Friday.”

US State Department spokesman Mark Toner said Washington was alarmed by the violence and “deeply concerned by the Syrian government’s use of violence, intimidation and arbitrary arrests to hinder the ability of its people to freely exercise their universal rights.”

Heavy shooting rattled Daraa throughout the day, and an Associated Press reporter in the city heard bursts of semi-automatic gunfire echoing in its old center in the early afternoon.

The London-based Syrian Human Rights Committee reported on its website, quoting sources in Daraa, that Syrian authorities shot and killed soldier Khaled al-Masri for refusing orders to take part in storming al-Omari mosque. The report could not be independently confirmed.

State TV said that an “armed gang” had attacked an ambulance in the city and security forces killed four attackers and wounded others and was chasing others who fled. It denied that security forces had stormed the mosque, but also showed footage of guns, AK-47s, hand grenades, ammunition and money that it claimed had been seized from inside.

- AP