"The drills carried out by our country in the northwest border areas... are a question of sovereignty," Iranian foreign ministry spokesman Saeed Khatibzadeh said in a statement on the ministry website.

Tehran "will take all measures it judges necessary for its national security", he said, adding, "Iran will not tolerate the presence of the Zionist regime near our borders" -- an allusion to Azerbaijan's relations with Iran's enemy Israel.

Azerbaijani President Ilham Aliyev had criticised Tehran over the drills, calling them "a very surprising event".

"Every country can carry out any military drill on its own territory. It's their sovereign right. But why now, and why on our border?" he said in an interview with Turkish news agency Anadolu published on Monday.

No further details were available on the military exercises.

Fighting broke out between Azerbaijan and Armenia in September last year over the disputed Nagorno-Karabakh region, claiming some 6,000 lives over six weeks.

A major supplier of arms to Azerbaijan, Israel came under diplomatic fire from Armenia over the struggle between the Caucasus neighbours.

Iran and Azerbaijan share a border of around 700 kilometres (430 miles) and enjoy good relations.

According to some estimates, there are around 10 million members of Iran's Azeri-speaking community.