AKCAKALE, TURKEY — Turkey and Syria fired artillery and mortars across their volatile border for a fifth consecutive day on Sunday, in one of the most serious and prolonged flare-ups of violence along the frontier.

The exchange of fire stoked fears that Syria’s civil war will escalate into a regional conflagration drawing in NATO member Turkey.

Turkish Foreign Minister Ahmet Davutoglu had warned on Saturday that Ankara would respond forcefully to each errant Syrian shell that lands on Turkish soil.

Ankara’s warning was coupled by an apparent diplomatic push by the Turkish leadership to promote Syrian Vice President Farouk al-Sharaa as a possible figure to head a transitional administration to end the conflict in the country.

In an interview with Turkish state television TRT Saturday, Davutoglu said that al-Sharaa was a figure “whose hands are not contaminated in blood” and therefore acceptable to Syrian opposition groups.