BAKU/YEREVAN -- A cease-fire in the breakaway region of Nagorno-Karabakh was under severe strain on October 20 after new clashes erupted between Azerbaijani and ethnic Armenian forces despite international pressure for the warring sides to halt the fighting.

A second cease-fire, agreed on October 17, has done little to slow the fighting that began last month, amid concerns it could spark a wider conflict involving Russia and Turkey and fears over the security of gas and oil pipelines in the South Caucasus.

In the latest diplomacy to resolve the crisis, Russian President Vladimir Putin and his French counterpart, Emmanuel Macron, discussed the situation in Nagorno-Karabakh during a phone call on October 20.

The two leaders said they agreed Armenia and Azerbaijan should relaunch "substantial negotiations" over Nagorno-Karabakh, a separatist enclave in Azerbaijan and controlled by ethnic Armenians, the Elysee said.

Separately, Azerbaijani Foreign Minister Ceyhun Bayramov and Armenia’s top diplomat, Zohrab Mnatsakanian, will both meet U.S. Secretary of State Mike Pompeo in Washington on October 23, the two foreign ministries said.

Bayramov and Mnatsakanian were not expected to meet face-to-face.

The United States, France, and Russia are the co-chairs of the so-called Minsk Group of the Organization for Security and Cooperation in Europe (OSCE), which has spearheaded efforts to resolve the dispute over Nagorno-Karabakh since a 1994 cease-fire.

International powers are scrambling to halt fighting and bring Armenia and Azerbaijan back to the negotiating table following three weeks of fighting that has killed hundreds of soldiers and civilians.

Two humanitarian cease-fires have failed to hold, with the latest fighting on October 20 spread along multiple fronts separating the two warring sides.

Officials in Nagorno-Karabakh reported artillery bombardments, with fighting particularly intense in southern areas of the conflict zone.

Azerbaijan's Defense Ministry also reported battles in several areas in and around the disputed territory.

Fears Of Humanitarian Crisis

There are fears of a looming humanitarian crisis as the fighting spreads to cities and towns in Nagorno-Karabakh and Azerbaijan, with infrastructure ruined, scores of civilians injured or killed, and thousands displaced.

Nagorno-Karabakh said on October 19 that 729 of its military personnel and 37 civilians had been killed in the fighting.

Azerbaijan said 61 Azeri civilians had been killed and 282 wounded. It has not disclosed its military casualties.

Azerbaijan, a close ally of regional power and NATO member Turkey, says it has made territorial gains both in Nagorno-Karabakh and some of the seven areas outside the region controlled by Armenian forces.

But Armenia, which has a defense pact with Russia, says it has repulsed Azerbaijani attacks and has the situation under control.

Internationally recognized as part of mainly Muslim Azerbaijan, the mountainous territory of Nagorno-Karabakh has been controlled by mainly Christian ethnic Armenians, backed by Yerevan, since the 1994 halt in fighting.

The latest fighting has stoked fears that the violence could engulf the region in a wider conflict involving Azerbaijan's closest ally, Turkey, and Russia, which dominates the Collective Security Treaty Organization, of which Armenia is a member.

With reporting by AP, Reuters, AFP, and TASS