BAKU, Azerbaijan

Armenian forces on Sunday launched a missile attack on the Khizi and Absheron regions of Azerbaijan, according to a senior presidential official.

Hikmet Hajiyev, the assistant to the president and foreign policy chief for Azerbaijan's presidency, said on Twitter that Armenian forces launched two 300-kilometer mid-range missiles on the regions.

Earlier, Haciyev announced that Mingachevir, an industrial city in Azerbaijan, had also been targeted by an Armenian missile strike.

Upper Karabakh conflict

Relations between the two former Soviet republics have been tense since 1991, when the Armenian military occupied Upper Karabakh, an internationally recognized territory of Azerbaijan.

Multiple UN resolutions, as well as many international organizations, demand the withdrawal of the invading forces.

The OSCE Minsk Group -- co-chaired by France, Russia and the US -- was formed in 1992 to find a peaceful solution to the conflict, but to no avail. A cease-fire, however, was agreed upon in 1994.

Many world powers including Russia, France, and the US have urged an immediate cease-fire. Turkey, meanwhile, has supported Baku's right to self-defense.