ISTANBUL — Syrian government attacks on Turkish positions in northwest Syria are driving Turkey deeper into the country’s civil war, prompting it to send reinforcements to the region and press for a Turkish-controlled military zone there.

Syrian troops killed eight Turkish soldiers and a civilian contractor last week and five more soldiers on Monday. Backed by Russian bombers, Syrian forces have encircled several Turkish observation posts in the northwestern province of Idlib — posts established by agreements aimed at reducing violence.

Turkey, which supports Syria’s opposition forces, has pushed back, pummeling the advancing Syrian units with artillery and killing dozens of Syrian troops and allied fighters, according to the Syrian Observatory for Human Rights, a London-based war monitor. A Syrian helicopter was shot down on Tuesday, reportedly by rebel forces.

The surge in fighting, as the Syrian government tries to retake the country’s last rebel-held province, has created the largest displacement of people in the war’s nine-year history. About 700,000 people have fled their homes in Idlib since December, the United Nations said Tuesday. Many are living in tents near the Turkish border, and there have been recent reports of children freezing to death.