A Turkish C-130 military cargo plane with at least 20 personnel on board crashed in Georgia on Tuesday after taking off from Azerbaijan, but the number of casualties and the cause of the incident were not immediately clear.

Initial video from the scene near the Azerbaijan border showed chunks of twisted metal strewn across a grassy knoll, with parts of the fuselage still ablaze and dark smoke rising into a clear sky. Fire engines stood nearby and a helicopter whirred overhead.

Footage circulating on social media appeared to show the plane corkscrewing towards the earth and then bursting into flames. Reuters could not immediately verify that footage.

Turkish President Tayyip Erdogan interrupted a speech in Ankara to offer condolences for “our martyrs” – a term he regularly uses to describe not only combat deaths but also service personnel killed during their general duties.

Erdogan, his office and the ministry did not say what caused the crash, and they did not provide a death toll. Local media said there were both Turkish and Azeri personnel on board the US-made aircraft but gave no numbers.

After a call with Erdogan, Azerbaijan’s President Ilham Aliyev said, according to an official readout, that he had discussed “the tragic news of the loss of servicemen” in the crash.