The weapons sale was sensitive as a long-running Azerbaijan-Armenia border conflict recently escalated into deadly clashes.

In a phone call with his Azerbaijani counterpart, President Aleksandar Vucic underlined Serbia's "friendship" and "strategic partnership" with the oil-rich country, according to a statement from the presidency.

Vucic invited President Ilham Aliyev for an official visit and sent a special envoy to Baku "to prepare the meeting".

A spat erupted in July when it emerged that Serbia was selling mortars and ammunition to Azerbaijan's foe Armenia during a fresh bout of violence.

The two ex-Soviet countries are locked in a decades-old conflict over the breakaway region of Nagorny Karabakh.

Serbia initially defended the private weapons sale as legal, but President Vucic later described the deal as a "wrong decision".

Azerbaijan is an important ally for Serbia, as Baku backs Belgrade's refusal to accept the independence of its former province Kosovo, which officially broke away in 2008.

Serbia's Interior Minister Nebojsa Stefanovic earlier met with the Azerbaijani ambassador and expressed "regret" for deaths among security forces in the recent fighting.

Stefanovic faced scrutiny last year after his father was linked to an arms trade scandal.

Some of the companies that have exported weapons to Armenia since 2018 are allegedly under control of Slobodan Tesic, a UN black-listed arms dealer, according to local investigative media.