Azerbaijan and ethnic Armenian forces fought new battles on Wednesday in the biggest eruption of their decades-old conflict since the mid-1990s, while France and Turkey traded recriminations as international tensions mounted.

Azerbaijan and the ethnic Armenian enclave of Nagorno-Karabakh said there were attacks from both sides along the line of contact that divides them.

In Wednesday's clashes, the latest in decades of conflict, Armenian media said three civilians had been killed and several wounded by shelling in the town of Martakert in Nagorno-Karabakh.

WATCH | Azerbaijan, Armenia intensify fighting over contested Nagorno-Karabakh region:

Azerbaijan said 14 Azeri civilians had been killed since fighting began on Sunday. Photographs taken in the Azeri town of Terter showed people taking cover in dugouts, and damaged buildings that residents said had been hit by Armenian shells.

Dozens have been reported killed and hundreds wounded in fighting that began on Sunday and has spread far beyond the enclave's borders, threatening to spill into all-out war between the former Soviet republics of Azerbaijan and Armenia.

Azerbaijan said ethnic Armenian forces attempted to recover lost ground by launching counter-attacks in the direction of Madagiz, but Azeri forces repelled the attack.

Armenia said the Azeri army had been shelling the whole front line during the night and two Azeri drones were shot down over Stepanakert, Nagorno-Karabakh's administrative centre. It was not possible to independently confirm the report.

The fighting has increased concerns about stability in the South Caucasus region, a corridor for pipelines carrying oil and gas to world markets, and raised fears that regional powers Russia and Turkey could be drawn in.

Some of Turkey's NATO allies are increasingly alarmed by Ankara's stance on Nagorno-Karabakh, a breakaway region inside Turkey's close ally Azerbaijan that is run by ethnic Armenians but is not recognized by any country as an independent republic.

WATCH | Clashes between Armenia, Azerbaijan intensify:

Turkish President Recep Tayyip Erdogan said on Monday Azerbaijan must take matters into its own hands and that Turkey would stand with it "with all its resources and heart." Foreign Minister Mevlut Cavusoglu reiterated Ankara's backing on Wednesday, saying Turkey would "do what is necessary" when asked whether it would offer military support if Azerbaijan requested it.

Cavusoglu criticized France, which has many citizens of Armenian ancestry, saying French solidarity with Armenia amounted to supporting Armenian occupation in Azerbaijan.

French President Emmanuel Macron hit back while visiting fellow NATO member Latvia.

Macron said France was extremely concerned by "warlike messages from Turkey, "which essentially remove any of Azerbaijan's inhibitions in reconquering Nagorno-Karabakh. And that we won't accept."

On Tuesday, Canadian Minister of Foreign Affairs François-Philippe Champagne and British Foreign Secretary Dominic Raab released a joint statement saying they are "deeply concerned by reports of large-scale military action" in the region.

"We call for the immediate end of hostilities, respect for the ceasefire agreement, and the protection of civilians."

The UN Security Council called on Tuesday for an immediate end to the fighting over Nagorno-Karabakh, which broke away from Azerbaijan in the 1990s in a war that killed an estimated 30,000 people and displaced hundreds of thousands.

Armenian Prime Minister Nikol Pashinyan, who spoke by phone to Russian President Vladimir Putin on Tuesday, said he was not considering asking for help under a post-Soviet security treaty now, but did not rule out doing so.

"Armenia will ensure its security, with the participation of the Collective Security Treaty Organisation (CSTO) or without it," Russian news agencies quoted Pashinyan as saying.

He said he and Putin had not discussed the possibility of Russian military intervention in the Nagorno-Karabakh conflict.

Russia has used the CSTO, along with the Eurasian Economic Union, another regional bloc focused on trade, to project influence across most of the former Soviet Union.

The Azeri prosecutor's office said on Wednesday seven more civilians had been wounded as a result of shelling of the city of Terter, which borders Nagorno-Karabakh.

Its defence ministry said ethnic Armenian forces attempted to recover lost ground by launching counter-attacks in the direction of Madagiz, but Azeri forces repelled the attack.

Armenia's defence ministry said the Azeri army had been shelling the whole front line during the night and two Azeri drones were shot down in the town of Stepanakert, Nagorno-Karabakh's administrative centre. It was not possible to independently confirm the report.