Syrian President Bashar Assad said Sunday that the state had "an obligation" to punish "outlaws" whom he accused of "terrorizing the population", according the official news agency Sana.
"Responding to outlaws who cut roads, shut down cities, and terrorize the population is an obligation of the state, which must defend national security and protect citizens' lives," Assad said.
The statement followed reports by an activist group saying Syrian troops killed 20 people in a tank assault on the eastern city of Deir al-Zor on Sunday, despite a direct UN appeal to Assad to stop using military force against civilians.
The attacks on the central town of Houleh in the Homs province and Deir el-Zour in the east early Sunday came a day after the country's foreign minister looked to allay protests demanding reforms by announcing that free parliamentary elections would be held by the end of the year.
Earlier the London-based Syrian Observatory for Human Rights said at least four people were killed when troops stormed Houleh, but the Local Coordination Committees, an activist group tracking the uprising, said seven people were killed in a bombing raid on the town. It was not immediately possible to reconcile the discrepancy.
An activist in the Deir el-Zour told The Associated Press the military launched a pre-dawn raid on the city, attacking it from four sides and so far taking control of eight neighborhoods. He said the raid began at 4 am, and the Local Coordination Committees confirmed that parts of the city were under the control of the military.
"Human conditions in the city are very bad since it has been under siege for nine days," the activist said on condition of anonymity, fearing reprisals. "There is lack of medicine, baby formula, food stuff and gasoline. The city is totally paralyzed."
The Deir el-Zour activist said he has no exact numbers of casualties, adding that many of the wounded cannot be taken to hospitals and are being treated in homes and mosques turned into clinics.
Turkey, which borders Syria, said Sunday it would send its foreign minister to Damascus on Tuesday to deliver a strong message against the crackdown on the protesters. Turkish Prime Minister Recep Tayyip Erdogan said his country's patience was running thin and that Turkey could not remain a bystander to the violence.
In addition, Gulf Arab countries broke their silence on the bloodshed, calling Saturday for an immediate end to the violence and for the implementation of "serious" reforms in Syria. In a statement posted on its website, the six-nation Gulf Cooperation Council expressed deep concern and regret for "the escalating violence in Syria and use of excess force."
UN Secretary General Ban Ki-Moon on Saturday urged Assad, in a phone conversation, to immediately stop the use of military force against civilians.
Deir el-Zour is the capital of an oil-rich province by the same name, but the region is among the country's poorest and was hit by drought in the past years. It is inhabited by Arab tribes that extend into Iraq, and Syrian authorities have said they thwarted attempts by locals to smuggle arms from Iraq into Syria.
Many of the tribes in the Deir el-Zour region were armed by Assad's regime in the past to fight members of the Syria's Kurdish minorities.
Reuters, AP, and AFP contributed to this report