The Syria government does not give death tolls for the conflict and says the rebels are terrorists backed by foreign powers who seek to destroy the country.
The Syrian conflict has split world powers, with the United States, Turkey and many European and Arab states calling for Assad to stand down. Russia, China and Iran have stood by the regime and criticized calls for Assad's ouster.
On Sunday, Turkish Prime Minister Recep Tayyip Erdogan visited Syrian refugees along Turkey's southern border, where he was joined by Mouaz al-Khatib, head of Syria's National Coalition.
Erdogan called for Assad to step down and said that Syria is experiencing "a holy birth."
"That holy birth is the coming to power of the will of the people," he said as refugees chanted his name.
Activists reported violence around Syria on Sunday.
Rebels in the north clashed with government troops near military bases in the provinces of Idlib and Aleppo and seized an oil pumping station in al-Raqqa.
The station receives crude oil from the nearby province of Hassakha and pumps it to one of Syria's two oil refineries in Homs, said Rami Abdul-Rahman, who heads the Syrian Observatory for Human Rights.
The Observatory also said rebels stormed a government air base in the area of Tel Hassir south of Aleppo, while government fighter jets launched deadly airstrikes near Aleppo, Hama and in a number of rebellious Damascus suburbs.
Activists also reported two car bombs in the Yarmouk district of Damascus, where most residents are Palestinian refugees.
Associated Press writers Suzan Fraser in Ankara, Turkey, and Sarah El Deeb in Cairo contributed to this report.