Azerbaijan’s parliament on Sunday declared a state of war in some of its cities and regions following Armenia’s border violations and attacks in the occupied Nagorno-Karabakh region.

In an extraordinary meeting, the National Assembly passed a measure partially and temporarily restricting the constitutional and property rights and freedoms of Azerbaijani citizens and foreigners in the country as long as the war situation continues.

Under the decision, a curfew may also be declared at certain times in some regions.

Border clashes broke out earlier Sunday after Armenian forces targeted Azerbaijani civilian settlements, and military positions. The number of casualties is not yet known.

Armenia has again proven that it is the biggest obstacle to peace and stability in the region, said Azerbaijan’s Defense Ministry in an earlier statement, adding that Turkey will stand with Azerbaijan by all means.

Baku has the right of self-defense to protect its people and territory, it added.

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

Four UN Security Council and two UN General Assembly resolutions as well as many international organizations demand the withdrawal of the occupying 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.

Armenia Declares Martial Law, Full Mobilization Amid Nagorno-Karabakh Escalation

The Armenian cabinet has declared martial law and a full mobilization of citizens as a result of the escalating tensions in the disputed region of Nagorno-Karabakh, the Armenian prime minister Nikol Pashinyan said on Sunday.

"Based on a decision by the government, martial law and a full mobilization have been declared in the Republic of Armenia. These decisions take effect immediately after official publication. I urge all personnel attached to the military to report at their territorial military commissions," Pashinyan wrote in a Facebook post.

Military clashes between the armed forces of Armenia and Azerbaijan broke out along the line of contact in Nagorno-Karabakh in the early hours of Sunday morning. Both sides have accused the other of targeting civilian settlements.

Armenia's Prime Minister Says Yerevan May Recognize Nagorno-Karabakh's Independence

The decades-old frozen Armenian-Azeri conflict in the breakaway region of Nagorno-Karabakh exploded into large-scale military clashes on Sunday, with each side blaming the other for the escalation.

Armenian Prime Minister Nikol Pashinyan has announced that Yerevan may grant formal diplomatic recognition to the self-proclaimed Republic of Artsakh, the de facto independent, Armenian-controlled region of Azerbaijan better known as Nagorno-Karabakh.

"The question of [Artsakh's] recognition is on our agenda. We must very seriously consider whether we are taking this step or not," Pashinyan said, speaking at an emergency session of the Armenian parliament on Sunday.

The prime minister added that Yerevan is considering "all scenarios for the development of events."

Pashinyan's announcement came following a major escalation of tensions between the self-proclaimed Artsakh Republic and Azerbaijan on Sunday morning, with both sides accusing the other of starting the conflict, which has led to numerous civilian and military casualties. 

The Republic of Artsakh is a breakaway state not recognized by any member of the United Nations, but which has unofficial support from Armenia and maintains unofficial diplomatic offices in Yerevan, as well as Russia, the United States, France, Australia, Lebanon and Germany. Formally, the Nagorno-Karabakh region which the Republic of Artsakh has de facto control over remains part of Azerbaijan.

The Nagorno-Karabakh conflict began in 1988 with the unleashing of nationalist sentiment in both Armenia and Azerbaijan by Soviet leader Mikhail Gorbachev's perestroika reforms. Lawmakers from the Nagorno-Karabakh Autonomous Region announced their secession from within the Azerbaijani republic of the USSR, while the Azerbaijani parliament in Baku formally abolished the region's autonomous status in late 1991. The Armenian and Azerbaijani armed forces and militias waged a full-scale war for the territory between 1992 and 1994, with the conflict ending in the wholesale takeover of the region by Armenian forces. Russia facilitated a shaky ceasefire in 1994, but deadly clashes have continued to flare from time to time in the years since. Over one million people from Nagorno-Karabakh and other areas of Armenia and Azerbaijan were displaced as a result of the conflict, with as many as 42,000 soldiers, militiamen and civilians from both sides killed during the war and in the sporadic clashes that took place in the years that followed.