BRUSSELS/PARIS (Reuters) – NATO will investigate French accusations that Turkey’s navy failed to respond to an allied call for inspection this month in the Mediterranean, the alliance chief said on Thursday, an incident Paris suspects involved Turkish arms smuggling to Libya.

France’s armed forces minister brought up the incident during a meeting of NATO defence chiefs at a time when the two allies have traded barbs over the crisis in Libya, accusing each other of supporting opposing sides in the country’s war.

Paris has repeatedly accused Ankara of violating a U.N. arms embargo. Turkey rejects the French accusations and has denied that the incident as described by France ever occurred.

Armed Force Minister Florence Parly said that on June 10 Turkish warships flashed their radar lights three times at the French warship Courbet in the eastern Mediterranean.

She said the Courbet was on a NATO mission to check whether a Turkish vessel, the Cirkin, was smuggling arms to Libya after it turned off its transponder, failed to identify itself and did not give its final destination.

She added that Turkish sailors had also put on bullet-proof vests and stood behind their light weapons during the incident.

“There cannot be any complacency with regard to such behaviour. This particularly serious incident must be dealt with and our allies share our concerns because eight European allies gave me clear support today in NATO,” Parly told French lawmakers after the ministerial meeting.

“This act was extremely aggressive and cannot be one of an ally facing another ally who is doing its work under NATO command,” she said.

NATO Secretary-General Jens Stoltenberg told a news conference that the incident was addressed at the meeting by several alliance states. “My message is that we have made sure that NATO military authorities are investigating the incident to bring full clarity into what happened,” he told reporters.

A senior Turkish official on Wednesday rejected the accusation and said French forces had sought to search a Turkish vessel in international waters “and this was not permitted”. He denied that Turkey had taken provocative or aggressive action to prevent this.