A Turkish C-130 military cargo plane with at least 20 personnel on board crashed in Georgia after taking off from Azerbaijan on Tuesday, as authorities reported an unspecified number of casualties and said rescue workers were headed to the site.

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 in the course of their general duties.

Erdogan, his office and the ministry did not say what caused the crash, and they did not provide the number of casualties. Local media said, without citing numbers, that there were both Turkish and Azeri personnel on board.

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, which happened near Georgia's border with Azerbaijan.

Turkey's Defence Ministry said 20 Turkish personnel were on board, including the flight crew, but provided no additional details on possible passengers of other nationalities.

Turkey and Georgia said they were working to reach the site.

Erdogan was handed a note by his aides as he was finishing a speech in Ankara.

"God willing, we will overcome this crash with minimum hardships. May God rest the soul of our martyrs, and let us be with them through our prayers," he said.

Georgia's Interpress news agency said the plane had crashed in Sighnaghi, a municipality in the Kakheti region in eastern Georgia, bordering Azerbaijan. It said the incident was being investigated.

US firm Lockheed Martin (LMT.N) which makes the C-130 Hercules that is widely used by air forces around the world, did not immediately respond to a request for comment.

The C-130 Hercules is a cargo, troop and equipment carrier aircraft. It is described as a four-engine, turboprop military transport aircraft that can make use of unprepared runways for takeoffs and landings.

Its versatile airframe has enabled it to be used for other purposes as well, including as a gunship and for airborne assault and reconnaissance operations. It is now viewed as one of the main tactical airlifters for many militaries.