Libya’s internationally recognized Prime Minister Abdullah al-Thinni accused Turkey last month of sending weapons to his Islamist rivals who seized the Libyan capital of Tripoli last year. “Turkey is a state that is not dealing honestly with us,” he told Egyptian television. “It’s exporting weapons to us so the Libyan people kill each other.”

These accusations are not new. In January, the speaker of Libya’s Parliament claimed , “Turkey still supports the terrorist militias in Libya.” In December, a prominent Benghazi-based activist claimed that Ansar al-Sharia in Libya, a faction loyal to al-Qaeda that has carried out acts of political violence against the recognized Libyan government , is partially funded by “businessmen linked by trade ties to Turkey.” Two weeks ago, the acting interior minister of the embattled government in Tobruk claimed that Turkish and Qatari aircraft are flying in and out of the Mitiga air base, which is controlled by the opposing Dawn coalition, amounting to “clear and explicit support” for terrorism in Libya.

The Libyan Civil War, which began after Qaddaffi’s fall, is often described as a proxy war, with Egypt and the United Arab Emirates reportedly backing al-Thinni and the officially recognized government in Tobruk, and Qatar and Turkey reportedly backing the Islamists and other opposition factions. Turkey has made no secret about backing the country’s Islamists after Qaddaffi’s fall in 2011, and it openly liaises with the self-declared Islamist government in Tripoli. Yet Turkey’s Libyan envoy complains that these latest allegations are a “ dangerous smear campaign .”

While hard evidence is still elusive, specific reports of Turkey’s growing role in the conflict began in January 2013, when Turkey’s Hurriyet newspaper reported that Greek authorities found Turkish weapons aboard a ship that was headed for Libya after the vessel stopped in Greece due to bad weather. In December of that year, the Egyptian press also reported that the Egyptian customs intercepted four containers of weapons from Turkey believed to be destined for Libyan militias.

The following year, in August 2014, the pro-Tobruk government’s Operation Dignity’s military commander, Khalifa Hifter, reportedly ordered his forces to shell a ship heading to the Libyan port of Derna carrying a cache of weapons from Turkey. Three months later, Turkish media reported in November 2014 that Greek authorities found 20,000 AK-47s in a ship heading from Ukraine to Libya. The Turkish captain said the ship was headed to Turkey’s southern Hatay port, but Libyan authorities said that maritime traffic data indicated that it was bound for Libya.

The following month, according to a Lebanese press report , Libyan authorities intercepted a Korean steamer headed to the embattled port city of Misrata that reportedly embarked from Turkey. The ship was carrying containers of weapons and ammunition allegedly intended for Islamist militias.

Another purported weapons route for Turkish weapons may lie to Libya’s southeast. In January, a Libyan military official claimed that both Turkey and Qatar were supplying Operation Dawn with weaponry through Sudan, which has long been a transit point for Iranian weaponry to extremist groups across the Middle East. Interestingly, when the government banned Turkish planes from Libyan airspace in January, it also announced that Sudanese planes were no longer permitted.

Whether by land or by sea, any delivery of lethal aid constitutes a direct contravention of the UN arms embargo . A recent United Nations report found that Turkey was one of more than a dozen countries — including Belarus, Greece, Hungary and Ukraine—that have been involved in shipping tons of munitions to Libya’s rival factions despite the embargo. The report notes that violations of the embargo not only threaten Libyan security, but also represent “a significant security challenge for other countries in the region, particularly from a terrorism perspective.”

In the meantime, Turkey also appears to be providing shelter to Libya’s jihadists. In January, Ansar al-Sharia, a Libyan Islamist militia, confirmed the death of its leader Mohamed al-Zahawi at a Turkish hospital, where he had received medical treatment for an “injury sustained in battles for Benghazi.” Turkey sent his body back to Misrata for burial.

We still only have a partial picture of what appears to be Turkish material support to Libya’s Islamists. Nonetheless, two U.S. government officials have told the Foundation for Defense of Democracies that this is an area of genuine concern. One former official notes that Turkish military assistance to the Islamist factions was simply “assumed.”

Whatever Turkey is doing, it has got the Tobruk government on high alert. The Libyan Air Force warned in January that it would attack any Turkish planes entering Libyan airspace. More recently, the Libyan government announced it would “exclude Turkish firms from operating in Libya.” To put this punitive measure into perspective, the volume of bilateral trade between Turkey and Libya in 2014 was $2.3 billion.

If Turkey were backing Libya’s jihadists, it would fit a dangerous pattern of Turkish support to extremist regional actors. After helping Iran to evade sanctions , allowing Hamas to establish a headquarters in Turkey, and embracing a permissive border policy that the Islamic State has exploited, Turkey now has even more to explain.

Jonathan Schanzer, a former U.S Department of Treasury analyst, is vice president for research at the Foundation for Defense of Democracies.