(CNN) -- Syrian troops rolled into the northwestern city of Saraqib early Thursday morning, just hours after evening prayers there called for an end to President Bashar al-Assad's reign, an opposition group said.
This came as world powers scurried to find a solution to the five-month-long crisis engulfing the country. At least eight people were killed on Thursday in the ongoing security crackdown on anti-government demonstrators, activists said.
In the latest diplomatic development, U.S. President Barack Obama and Turkish Prime Minister Recep Tayyip Erdogan underscored the "urgency of the situation" during a phone call on Thursday, the White House said in a statement.
Though U.S. officials have condemned the actions of al-Assad, Secretary of State Hillary Clinton has not called for him to step down.
"We are, I think, building the -- chorus of international condemnation," she told CBS News. "Rather than us saying it and nobody else following, we think it's important to lead and have others follow as well."
Meanwhile, the violence continued. In Saraqib, residents reported hearing heavy gunfire and seeing troops break down doors of local businesses during a search of the city for opposition activists, the Syrian Observatory for Human Rights said.
About 200 people had been arrested in Saraqib since troops seized the city earlier in the day, according to the Syrian Observatory group, which cited reports from opposition activists in the city. The identities of the activists were withheld at their request out of concerns for their security.
The site of the latest military action is Idlib province -- whence thousands fled their homes in Jisr al-Shugur for Turkey after the Syrian military took control of that town. The operation has raised concerns that thousands may again flee to Turkey to escape the crackdown.
Violence erupted in other towns and amid a growing chorus of international calls for Syria's government to end its brutal drive on peaceful protesters, the observatory said.
In al-Qusair, at the Syrian-Lebanese border, five people were killed; in the eastern city of Deir Ezzor, three people died during raids and some activists' homes were set afire, the observatory said.
There have been ongoing raids in the city of Daraa and a sit-in in Suwaida, both cities in the south, and heavy gunfire was heard in the Bab Amer neighborhod of the western city of Homs, according to the observatory.
Syrian forces had withdrawn from the center of the western city of Hama after troops laid siege to the city more than a week ago, Syria's state-run news agency said.
But the observatory said armored personnel carriers and machine guns mounted on vehicles remained in the city and 27 people have been detained.
Seventy-two journalists -- including some from the United States and France -- toured Hama Wednesday with permission from the government, the state-run Syrian Arab News Agency (SANA) reported. CNN was not among them; the government has limited access to the country by journalists in recent months.
Scores of people were killed during the siege that coincided with last week's start of the holy month of Ramadan, according to reports by opposition groups, including the Syrian Observatory and the Local Coordination Committees of Syria -- a loose coalition of groups that organize and document protests.
The conflict in Syria erupted five months ago when Syrian forces suppressed protests in the southern city of Daraa. Anti-government fervor caught on nationwide as more protests were met with tougher crackdowns.
By Wednesday, the death toll had reached 2,417 -- including more than 2,000 civilians, said the Local Coordination Committees of Syria.
CNN is not able to independently verify accounts of events on the ground or the death tolls.
As for Obama and Erdogan, they "reiterated their deep concern about the Syrian Government's use of violence against civilians and their belief that the Syrian people's legitimate demands for a transition to democracy should be met," the White House said.
"They agreed on the need for an immediate halt of all bloodshed and violence against the Syrian people. They further agreed to closely monitor the actions that the Syrian government is taking, and to consult closely in the days ahead."
CNN's Amir Ahmed, Arwa Damon, Nada Husseini and Yesim Comert contributed to this report.