UN Secretary General Ban Ki-moon warned on Monday that rising violence along the Syrian-Turkish border and the effect of the Syrian conflict on Lebanon were extremely dangerous.
"The escalation of the conflict along the Syrian-Turkish border and the impact of the crisis on Lebanon are extremely dangerous," Ban said at the opening of the World Forum for Democracy in the French city of Strasbourg.
Ban also urged donors to provide more funding to help deal with the humanitarian disaster in Syria.
"As winter approaches, we need donors to contribute more generously to address the growing needs of those inside Syria and over 300,000 refugees in neighbouring countries," he said.
The armed uprising in Syria has increasingly sparked violence on the country's border with NATO member Turkey, with the Turkish military returning fire on Sunday after a shell launched from Syria struck the border village of Akcakale.
There were no casualties in Sunday's incident, but last Wednesday five civilians had been killed in the village by a shell launched from Syria.
Since Wednesday, the Turkish military has responded in kind whenever Syrian ordnance has breached its territory, inflaming tensions between the former allies and leading to fears of a broader conflict.
The Turkish parliament last week gave the government the green light to use military force against Syria if necessary, while the UN Security Council strongly condemned cross-border attacks by Syria and called for restraint.