Border clashes erupted again early on Thursday between arch-foes Azerbaijan and Armenia, officials in both countries said, following a pause in fighting amid a flare-up over a decades-long territorial dispute.

At least 16 people on both sides have been killed since border clashes erupted on Sunday between the ex-Soviet republics, which have been locked for decades in a conflict over Azerbaijan's separatist region of Nagorny Karabakh.

The territory was seized by ethnic Armenian separatists in a 1990s war that claimed 30,000 lives, though the recent fighting broke out on a northern section of their shared border far from Karabakh.

Azerbaijani forces were "shelling Armenian villages with mortars and howitzers," Armenia's defence ministry spokeswoman Sushan Stepanyan said on Thursday.

"The fire still continues," she wrote on Facebook.

Map of Azerbaijan and Armenia locating the Armenian province of Tavush where border clashes occurred
Map of Azerbaijan and Armenia locating the Armenian province of Tavush where border clashes occurred AFP / STAFF

The defence ministry in Baku said in a statement that clashes were ongoing in the north after "Armenians shelled Azerbaijani villages with large-calibre weapons."

The renewed violence erupted after both sides observed a pause in fighting on Wednesday.

The clashes that broke out last week have raised fears of a major flare-up in the strategic Caucasus region and prompted calls for an immediate de-escalation from the United States, the European Union and regional power broker Russia.

Internationally mediated peace talks between the two Caucasus nations have so far failed to bring about a solution to their territorial dispute.

Energy-rich Azerbaijan has repeatedly threatened to win control over Karabakh by force after seeing diplomatic efforts to reclaim the territory fail.

Armenia has vowed to crush any military offensive.

Russia