PARIS — The UN’s secretary-general on Monday made a strong appeal to halt the flow of arms into Syria and warned that the crisis threatens stability in the entire region.

Ban Ki-moon said he is “deeply concerned” about the continued flow of arms to both the Syrian government and opposition forces, and said a “political solution” is “the only way out of the crisis.”

Speaking at an international conference on democracy in Strasbourg, the UN chief described as “extremely dangerous” the escalating conflict along the Syrian-Turkish border and the crisis’ impact on Lebanon.

In his speech Monday to the World Forum for Democracy Ban also said the UN-Arab League envoy to Syria Lakhdar Brahimi would return to the region this week to continue international efforts seeking political transition in Syria.

Turkish Prime Minister Recep Tayyip Erdogan on Sunday warned Damascus against starting a war with Turkey, saying that it would be a great mistake on Syria’s part. Speaking at a conference in Istanbul, Erdogan said that Turkey needs “to be prepared as if you are about to be in a war at any time,” according to Hurriyet Daily News.

Opposition groups reported that at least 40 Syrians were killed in clashes with government forces on Monday. Thirty of the slain were killed when Assad troops shelled a vehicle carrying wounded Syrians near the southern city of Daraa.