NATO Secretary-General Jens Stoltenberg said on Tuesday the indications available so far were that a drone which crashed in Zagreb last Thursday was unarmed and that it was not an armed attack.

Asked about the incident, Stoltenberg said at a press conference that the preliminary information available so far indicated it was not an intentional attack, but that such cases were also dangerous, so NATO increased surveillance.

A Soviet-made unmanned aerial vehicle crashed in a residential area in Zagreb shortly after 11 pm last Thursday, having entered Croatia’s airspace from Hungary and Hungary’s from Romania.

Stoltenberg recalled that he discussed the incident with Croatian Prime Minister Andrej Plenkovic on Sunday.

The alliance’s secretary-general said the investigation was still under way and the facts were being established, but the indications so far were that the drone did not carry a bomb nor explosive but was a reconnaissance drone.

The drone ran out of fuel and crashed in Zagreb, he added.

Stoltenberg also said that Croatia, Hungary and Romania were yet to exchange all information on this incident and cooperate more closely.