BAKU/YEREVAN - Several Azeri soldiers have been killed and Armenian soldiers and police wounded in border clashes, both countries said Monday, each accusing the other of encroaching on its territory.

The two former Soviet republics have long been in conflict over Azerbaijan's breakaway, mainly ethnic Armenian region of Nagorno-Karabakh, although the latest clashes occurred around the Tavush region in northeast Armenia, some 300km (190 miles) from the mountainous enclave.

The Azeri defense ministry said four of its soldiers had been killed and five wounded while Armenia's ministry said three of its soldiers and two police officers had been wounded in the clashes.

The exchanges of fire began Sunday and continued into Monday. The two sides traded accusations of cease-fire violations and shelling.

Azeri President Ilham Aliyev accused the Armenian leadership of a "provocation."

Armenian Prime Minister Nikol Pashinyan said the leadership of Azerbaijan would be responsible for "the unpredictable consequences of the regional destabilization."

The Organization for Security and Cooperation in Europe (OSCE), a security watchdog that has tried to help find a solution to the conflict, urged the two countries to speak to each other to prevent any further escalation.

The U.S. State Department condemned the violence, urged the two sides to stop using force immediately, and said it would "remain actively engaged in efforts" to achieve a peaceful settlement.

Nagorno-Karabakh, a mountainous part of Azerbaijan, is run by ethnic Armenians, who declared independence during a conflict that broke out as the Soviet Union crumbled in 1991.

Though a ceasefire was agreed in 1994, Azerbaijan and Armenia continue to accuse each other of shooting attacks around Nagorno-Karabakh and along the separate Azeri-Armenian frontier.

The frozen Nagorno-Karabakh conflict has concerned the international community in part because of its threat to stability in a region that serves as a corridor for pipelines taking oil and gas to world markets.