On Saturday, the former Soviet republic of Azerbaijan asked Iran’s ambassador in Baku to appear before them following an incident where an Iranian fighter jet purportedly approached and then crossed the Azerbaijani border.

Azerbaijan’s foreign and defense ministries reported that from 09:44 to 10:26 local time Saturday, an Iranian aircraft flew along the boundary between Azerbaijan’s Zangilan and Bilasuvar districts.

The announcement confirmed that the plane was traveling a distance of three to five km (two to three miles) from the country’s border and, at times, flying across the international border.

The Republic of Azerbaijan called on Iran’s ambassador to the nation to register their complaint over the occurrence. Reports were shared by Iranian state media. However, Tehran has yet to issue a response.

Azerbaijan’s government released a statement denouncing the military aircraft that had flown for over thirty minutes in the recently reclaimed areas, calling it a “provocation and unfriendly behavior.”

The two nations, whose border is approximately 700 kilometers (430 miles) long, have a complicated relationship.

The Iranian government is cautious of Azerbaijan’s strong ties with Israel, an expansive arms dealer to Baku. Additionally, Tehran is concerned about nationalists in Azerbaijan and its close ally Turkey who appear to be encouraging separatist movements among the large Azeri population.