The Syrian government said on Wednesday that German special forces were present, alongside French and American military personnel, in northern Syria, an accusation denied by Germany.
Syrian state media said the government strongly condemned the presence of French and German forces in Ain al-Arab, also known as Kobani, and Manbij.
"Syria … considers it explicit and unjustified aggression towards [Syria's] sovereignty and independence," state news agency SANA quoted the foreign ministry as saying.
The U.S.-backed Syria Democratic Forces (SDF) are staging an offensive against Islamic State near Manbij, while Kobani is under the control of the Syrian Kurdish YPG militia, part of the SDF.
Germany's defense ministry said repeated claims by the Syrian government that German special forces were in northern Syria were not and had never been true.
"There are no German special forces in Syria. The accusation is false," a ministry spokesman said.
The Britain-based Syrian Observatory for Human Rights, which monitors the Syrian civil war now in its sixth year, said French special forces were building a base for themselves near Kobani.
France's defense minister said last week that there were special forces operating in Syria helping the SDF advance towards Manbij.
The Observatory also said German, French and American military advisers, and French and American special forces, were assisting the SDF in its fight against Islamic State but had so far remained in a support role and not fought on front lines.