The army said troops seized the villages of Latamneh, Latmeen, Kfar Zeita and Lahaya, as well as the village of Morek, where Turkey maintains an observation post, pressing ahead its offensive toward Idlib.
The army advance represents the latest in a series of losses for rebels who have, for eight years, fought to topple Assad. It leaves his forces poised to focus on reclaiming Idlib province, near the border with Turkey, the last territory controlled by the opposition.
The Syrian Observatory for Human Rights also reported Friday that government troops were in control of the entire northern Hama countryside after capturing a series of towns and villages. Syrian TV showed troops walking freely inside these villages. An army statement said the military was removing mines and booby-traps left behind by the insurgents.
The fate of Turkish troops manning the observation post wasn't immediately clear. Since a deal with Russia last year, Turkey has maintained 12 such posts in and around Idlib province. Turkey is a strong backer of the Syrian opposition and rebels fighting Assad's forces, while Russia supports Assad's government.
The Observatory said it was not clear whether there were any Turkish soldiers remaining in the Morek observation post or whether they had withdrawn from the area overnight. Turkish Foreign Minister Mevlut Cavusoglu denied any Turkish troops were besieged in Syria. Speaking to reporters in Beirut on a visit, he said there were clashes in Idlib near Turkish observation posts "but we do not have any encircled soldiers."
He appealed for a political solution to the long-running Syria crisis that would put an end to more displacement and allow for the safe return of Syrian refugees. Turkey hosts around 3.6 million Syrian refugees and is concerned that the fighting in Idlib is causing a surge of displacement toward its sealed border with Syria.
On Friday, Turkish President Recep Tayyip Erdogan discussed the situation in Syria with Russia's Vladimir Putin, telling his Russian counterpart that violations of the cease fire in Idlib is paving the way to a "humanitarian crisis," according to Erdogan's office.
The Turkish leader also told Putin that the attacks were harming efforts for a resolution of the Syrian conflict and posing a "serious threat" to Turkey's security. Syrian troops, backed by Russian air cover, had laid siege to rebel-held villages in the central province of Hama earlier this week, following rapid advances.
Idlib, near the Turkish border, is the last major rebel-controlled province in Syria. Insurgents there have suffered a series of setbacks over the past three weeks in the face of a stepped-up government offensive in the country's northwest.
On Wednesday, government forces took control of the town of Khan Sheikhoun in Idlib province after an al-Qaida-linked group pulled out. They then launched the siege on rebel-held towns and villages in the northern province, adjoining Hama.
Syrian government forces have been on the offensive in Idlib and northern parts of Hama province since April 30, forcing nearly half a million people to flee to safer areas further north. The fighting also killed more than 2,000 people, including hundreds of civilians.
Associated Press writer Suzan Fraser in Ankara, Turkey, contributed reporting.