The Syrian army shot dead 11 people in a western town near the Lebanese border on Thursday and stormed a northwestern town near Turkey's border, activists said.
The shooting in the western town of Qusair also wounded many others, according to several Syrian human rights and activists groups.
Anti-government protests are common in Qusair and, combined with the early morning assault on the town of Saraqeb near the Turkish border, reflected the determination of President Bashar Assad to crush the five-month old uprising despite mounting international condemnation.
The U.S. imposed new sanctions on Wednesday, and a flurry of foreign diplomats have rolled through Damascus urging Assad to end a campaign of killing that rights groups say has left about 1,700 dead since mid-March. Turkey's foreign minister, a day after meeting with Assad, on Wednesday renewed his condemnation of the attacks.
The White House said President Barack Obama spoke with Turkish Prime Minister Tayyip Erdogan to underscore his deep concern about the Syrian government's use of violence against civilians.
It said the two agreed on Thursday that the violence in Syria must stop and that the demands of the Syrian people for a transition to democracy must be met. Obama and Erdogan agreed to consult closely on the situation in the coming days.
A U.S.-based international human rights groups released a report Wednesday night accusing Syrian authorities of targeting medical facilities, health workers and their patients. It called on the government to safeguard doctors' obligations to provide neutral and ethical care for civilians.
Physicians for Human Rights said security forces control access to hospitals, and many injured civilians in need of critical care are forgoing treatment because they fear being detained and tortured if they seek care at government-controlled medical facilities.
"In addition to the widely reported atrocities committed by the government, PHR has received reports of serious violations of medical neutrality in Syria," a statement by the group said.
It also quoted a group of Syrian physicians as saying 134 doctors have either been detained by the government or have disappeared.
In a continuing nationwide campaign of arrests, Syrian activists said Thursday that security forces detained Abdul-Karim Rihawi, the Damascus-based head of the Syrian Human Rights League. A longtime rights activist, Rihawi had been tracking government violations and documenting deaths in Syria.
The attack on Saraqeb is particularly noteworthy because it sits in Idlib, a province bordering Turkey. Intense protests in the area triggered a harsh government response, forcing hundreds of Syrians to flee across the border. The military on Wednesday said it withdrew from residential districts in the area and returned to its barracks.
The military also said this week it withdrew from Hama in central Syria, following a weeklong military siege and military operations in the defiant city.
A group of Turkish journalists who toured Hama for four hours Thursday saw two APCs parked at the main square keeping watch over the city center and soldiers on some streets, but no tanks or heavy weaponry in sight.
"The soldiers and security forces destroyed everything, they didn't leave anything. We are in God's hands," one man they spoke to said, speaking on condition of anonymity for fear of reprisal.
Another person said everything was calm and urged residents who escaped Hama to return.
In Saraqeb, troops detained at least 100 people, according to the London-based Syrian Observatory for Human Rights. Explosions and gunfire reverberated through the area after the army rolled in, said the Local Coordination Committees, an activist group that helps organize and document the protests.
The military action came a day after the information ministry ferried local journalists to Idlib. A senior army officer told reporters that troops were withdrawing to their barracks, leaving residential districts in the province's cities.
On the same day, Syrian security forces shot dead at least 15 people in the central flashpoint city of Homs, according to the LCC.
The government justified its attacks on various cities by saying it was dealing with terrorist gangs and criminals who were fomenting unrest.
The uprising was inspired by the revolutions and calls for reform sweeping the Arab world, and activists and rights groups say most of those killed have been unarmed civilians. An aggressive new military offensive that began with the Ramadan at the start of the month killed several hundred people in just one week.
The London-based observatory said authorities on Wednesday night detained opposition figure Hassan Zahra during a raid in a Damascus suburb. Zahra, a 67-year-old member of the Communist Action Front, was detained at least once since the uprising began, it said.
International condemnation over the crackdown has been strong, and growing more forceful.
In Turkey, Foreign Minister Ahmet Davutoglu renewed calls Thursday for an end to the bloodshed and said Turkey would be closely watching developments there.
"Of course, it is difficult to expect this when tensions are so high, but our expectation is that measures are taken to prevent the loss of lives, for civilian losses to end. We will be monitoring closely."
The Obama administration, which announced new sanctions Wednesday, is preparing for the first time to explicitly call for Assad to step down, officials have told the AP. The moves are a direct response to Assad's decision to escalate the crackdown by sending the army into opposition hotbeds.
The new sanctions affect the state-owned Commercial Bank of Syria and its Lebanon-based subsidiary, the Syrian Lebanese Commercial Bank, for what the U.S. says are their links to human rights abuses and to illegal weapons trade with North Korea.
Mobile phone company Syriatel was targeted because it is controlled by "one of the regime's most corrupt insiders," said David Cohen, the U.S. Treasury Department's undersecretary for terrorism and financial intelligence.
The action freezes any assets the firms have in U.S. jurisdictions and bans Americans from doing business with them. But they may not have much immediate economic impact because the U.S. already severely limits trade and economic ties with Syria.
APTN producer Ayse Wieting and cameraman Mehmet Guzel contributed to this report from Hama, Syria.
Bassem Mroue can be reached at http://twitter.com/bmroue