Syrian rights groups say government troops backed by armored vehicles have killed at least 53 people in assaults on two towns where civilians have protested President Bashar al-Assad's autocratic rule.

The rights groups say at least 42 people were killed Sunday after Syrian forces launched a pre-dawn raid on the eastern town of Deir el-Zour. They say another military assault on the central town of Houleh killed at least 13 people.

Syrian President Bashar al-Assad defended his violent crackdown, saying Sunday it is a “national duty” to deal with what he calls “outlaws” who cut off roads and “terrorize” people. Speaking during talks with Lebanon's visiting foreign minister, Mr. Assad also said Syria is on a path to reform.

The Syrian president is facing growing international pressure to end the crackdown. The Arab League called on the Syrian leader to stop the violence “immediately” on Sunday — the first time it has issued such a statement since the revolt began in March.

The United Nations says Secretary-General Ban Ki-moon gave the same message to Mr. Assad in a phone call on Saturday.

Turkish Prime Minister Recep Tayyip Erdogan said he has run out of patience with Syria's crackdown and will send Foreign Minister Ahmet Davutoglu to Damascus on Tuesday to deliver that message in a “decisive” manner.

Mr. Assad's adviser Buthaina Shaaban criticized Turkey on Sunday, saying it failed to condemn armed groups whom Damascus says have brutally murdered Syrian civilians and security forces. She said Syria will make that point to Davutoglu in an even stronger manner.

In the Syrian government's latest gesture to opposition protesters, Foreign Minister Walid Moallem said Saturday authorities will hold free parliamentary elections by the end of this year. Opposition activists have dismissed such gestures in the past.

The United States says Mr. Assad's security forces are responsible for the deaths of more than 2,000 people in the uprising.