A shooting on the Iran-Azerbaijan border has led to the border being closed for several days, the latest episode of tension between the two countries. The controversy began last week, when an unidentified gunman (in military uniforms, according to Azerbaijan) fired shots at a tractor working on the shore of the Araz River that forms the border between the two countries.

No one was injured, but in response, "The Azerbaijani side accused the Iranian military of the fire and demanded an explanation. Not having received them, the Azerbaijani authorities closed the nearest border crossing point Shahtakhti," near the site of the incident in Azerbaijan's Nakhcivan exclave. And then Iran retaliated by closing off the other two border crossings in Nakhvican, citing "Baku's refusal to negotiate over the issue." From Press TV:

[Iranian embassy in Baku press secretary Mohammad] Ayatollahi said Azerbaijan sealed the border crossing in an “unconventional move” on Wednesday after an unidentified assailant opened fire on a tractor in the border region without causing any casualties.

He stated that the border closure has created serious problems for Iranian passengers and drivers....

He stated that an Iranian border guard was killed by Azeri security forces in Bileh-Savar two years ago, but Iran did not close the border and pursued the issue through the relevant authorities.

The tension has gradually dissipated, and pedestrians have been allowed through, but the border remains closed to vehicles. On Monday, Iran's ambassador in Baku said the border would be reopened "soon" and talked up the "strategic and friendly" relations between the two countries. But the fact that such a small incident has blown up like this speaks to the heavy distrust between Baku and Tehran.