Turkey and Russia have launched joint patrols in Idlib province, the Syrian opposition's last major bastion in the country.
Turkish Defence Minister Hulusi Akar told reporters on Friday that the operation followed an agreement made in September last year that was aimed at preventing the Syrian government from launching an attack on Idlib - home to nearly three million people.
Idlib province is the last major area held by Syrian rebels and is controlled by Hay'et Tahrir al-Sham (HTS), which was previously affiliated to al-Qaeda.
According to the agreement, Russian forces would patrol the edge of the rebel-held province while the Turkish army would operate in the demilitarised zone.
"There were restrictions on the use of Idlib and Afrin regions' airspace but these have been lifted from today," Akar said, adding that the patrols marked "a significant step" for the continuation of ceasefire and maintaining stability in Idlib.
"Our cooperation with Russia has improved. We see this as a significant step for the continuation of the ceasefire and ensuring stability".