BEIRUT — Syrian security forces opened fire on protesters Friday, killing at least 16 people as thousands joined demonstrations across the country calling for an end to President Bashar Assad's regime, witnesses and activists said.
International condemnation is growing as the uprising enters its seventh week with no end in sight. More than 580 civilians and 100 soldiers have been killed since the revolt began, rights groups say.
On Friday, U.N. Secretary-General Ban Ki-moon said Syria has agreed to allow U.N. teams to enter the country and check the humanitarian situation. A European Union official said the bloc's member nations have agreed to place sanctions on Syria next week.
The protesters turned out Friday despite a bloody crackdown on the uprising and some of the tightest security seen since the protests began in mid-March.
"We were chanting, peaceful, peaceful and we didn't even throw a stone at the security forces," said a witness in the central city of Homs, who said some 10,000 people were in the streets. "But they waited for us to reach the main square and then they opened fire on us."
He said gunshots rang out even after the protesters dispersed.
"The bullets are like rain," he said. "Everyone is terrified."
Syrian authorities also detained Riad Seif, a leading opposition figure and former lawmaker who has been an outspoken critic of the regime during the uprising, according to the Syrian Observatory for Human Rights.
"Syria's authorities think that they can beat and kill their way out of the crisis," said Sarah Leah Whitson, Middle East director at Human Rights Watch. "But with every illegal arrest, every killing of a protester, they are precipitating a larger crisis."
Ten people were killed Friday in Homs and six were killed in Hama, said Ammar Qurabi, who heads the National Organization for Human Rights in Syria.
Footage posted on YouTube showed protesters in Hama frantically trying to resuscitate a man lying on the ground with a bloodied face and shirt, while people shouted "God is great!"
Rallies were held in major areas including the capital, Damascus, and its suburbs, Banias on the coast and Qamishli in the northeast.
"The people want to topple the regime!" protesters shouted, echoing the cries heard during the revolutions in Egypt and Tunisia.
In the Damascus suburb of Douma, scene of intense protests over recent weeks, security forces cordoned off the area to prevent anyone from entering or leaving.
A witness near Douma said he saw a train carrying about 15 army tanks heading north Thursday evening toward the central province of Homs.
Another activist in Damascus said hundreds of people marched in the central neighborhood of Midan. In Banias, witnesses said more than 5,000 people carrying olive branches and Syrian flags also were calling for regime change.
"Our morale is high, they cannot stop us no matter what they do and how many people they arrest," he said.
In the southern city of Daraa, where the army announced the end to an 11-day military operation Thursday, residents said troops were still in the streets, causing many to stay from a protest there on Friday.
"There's a tank stationed at each corner in Daraa. There is no way people can hold a protest today," a resident said by telephone. "It means more killing. Daraa is taking a break. We don't want to see more killing or face tank guns."
The activists spoke on condition of anonymity for fear of government reprisals.
The International Committee of the Red Cross said a medical team reached Daraa on Thursday with trucks carrying humanitarian goods and medical supplies. The ICRC had appealed to Syrian authorities earlier in the week to allow it to access to Daraa after being unable to reach the city previously while it was under siege by security forces.
Assad is determined to crush the revolt that has now become the gravest challenge to his family's 40-year dynasty. He has tried a combination of brute force, intimidation and promises of reform to quell the unrest, but his attempts have failed so far.
Security forces have repeatedly opened fire on protesters during rallies around the country in the past week and last Friday at least 65 people were killed, according to rights groups.
The mounting death toll — and the siege in Daraa — has only served to embolden protesters who are now demanding nothing less than the end of Assad's regime. There also has been growing international condemnation of the government's tactics.
Syria blames the unrest on a foreign conspiracy and "terrorist groups" that it says have taken advantage of protests.
The uprising in Syria was sparked by the arrest of teenagers who scrawled anti-regime graffiti on a wall in Daraa. Protests spread quickly across the nation of some 23 million people.
Assad inherited power from his father in 2000.