At least 28 were killed when tanks and helicopters opened fire in the northern town of Maarat al-Numan, activists told the BBC.
Syrian forces also entered the northern village of Jisr al-Shoughour Friday, and state television reported troops arrested members of "armed organizations," The New York Times reported.
"The army is invading the villages and burning the surrounding farms and killing people randomly," Hozan, a spokesman for the Local Coordinating Committees who asked that his last name be withheld, told the Times.
Demonstrations were organized for the first time Friday in Syria's largest city and economic capital, Aleppo, a development sure to confound the foundering government, The Washington Post reported.
"The government is confused. They don't know what to do," Razan Zeitouneh, a human-rights lawyer who is in hiding in Damascus, told the Post. "Each time they use violence, more people turn out to protest, and they are all calling for the regime to end."
Earlier Friday the Local Coordinating Committees told the Times residents of al-Sarmaneyah burned tires in the streets to slow the march of Syrian troops into Jisr al-Shoughour.
"The town is under siege by the army and security forces," the committee said in a statement.
A Syrian man at the refugee camp in Yayladagi, Turkey, told the Times other refugees in the camp spoke by phone with relatives near Jisr al-Shoughour and they reported a violent attack had begun.
"They are talking about the army moving with all kinds of armed vehicles and shooting randomly," the man said. "They are also burning the harvest and livestock on the streets. The army passed through al-Sarmaneyah and troops are shooting everyone who comes along their way. It is terrible there."
Turkish Justice Minister Sadullah Ergin, speaking Friday to reporters at the Yayladagi camp, repeated his call for Syria to end the violence against its citizens. Asked whether Turkey would participate in an international military intervention in Syria, Ergin said, "We don't even want to consider that possibility."
Syrian security forces amassed around Jisr al-Shoughour Thursday after clashes during the weekend made the area the new focal point of the popular uprisings that moved across Syria since March.
In Geneva, U.N. high Commissioner for Human Rights Navi Pillay called on Syria to stop the "assault on its own people."
Reports indicate more than 1,100 people had been killed and "10,000 or more" detained in the weeks since the unrest began, Pillay said, adding that the gathering of Syrian security forces in the northwest fueled concerns that the toll would rise.
An estimated 4,000 Syrians are seeking refuge in Turkey, the Post said.
"If such inflow continues, there could be a very serious humanitarian situation," Foreign Minister Ahmet Davutoglu said.
"Turkey is a powerful country," he said. "If a humanitarian situation develops, Turkey will do its best."
The Red Crescent, the Muslim equivalent of the Red Cross, provided tents at the border camps located about 30 miles south of the Turkish city of Antakya. Despite the Red Crescent efforts, some families spent the night in the open, The Wall Street Journal reported.
Turkey has a visa-free travel agreement with Syria and Turkish Prime Minister Recep Tayyip Erdogan pledged to honor it and to keep the Syrian border open.
"We will always keep our doors open to our Syrian brothers and sisters," he said on Turkish Radio.