At least 25 Syrians were shot dead by troops and security forces on Monday in the town of Daraa, 100 km to the capital Damascus, pan-Arab al-Jazeera TV reported.

A Syrian youth is hurling stones at an armored vehicle in the town of Daraa.

Hundreds of troops and security forces backed with tanks and armored vehicles entered the town Monday morning from four directions. The telecommunication and electricity were cut, an eyewitness told al-Jazeera.

State-run al-Ekhbaria TV reported that 10 soldiers were killed in an ambush set by an armed group while army troops were entering the town to impose stability.

U.S. President Barak Obama and Turkey Prime Minister Erdogan held a phone talk on Monday and expressed their deep concern about the Syrian government's 'unacceptable use of violence against Syrian people'.

They also called on the Syrian government to end the use of violence and promptly enact meaningful reforms that respect the democratic aspirations of Syrian citizens.

The U.S. government is considering a variety -- a range of options, including targeted sanctions against the Libyan government officials, the White House spokesperson Jay Carney told reporters on Monday.

"What we have seen is that sanctions can put pressure on governments and regimes to change their behavior," Carney continued.