BAKU/YEREVAN -- Armenia and Azerbaijan have accused each other of violating a new cease-fire aimed at stopping the fighting over the breakaway region of Nagorno-Karabakh.

The truce, which was announced on October 17 and took force at midnight, was the second attempt at establishing a cease-fire since heavy fighting erupted in the region on September 27.

The fighting has killed at least 600 soldiers and civilians and is considered the worst since the 1994 cease-fire that ended all-out war between the two countries over Nagorno-Karabakh’s status.

Josep Borrell, the EU’s top diplomat, called the foreign ministers of both nations on October 18 to condemn the continued fighting and urge them to stick to the cease-fire.

The fighting “leads to more civilian suffering. It aggravates the conflict between states and respective societies, rendering the healing of wounds even more difficult,” Borrell said in a statement after his phone calls.

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

The latest spasm of violence has stoked fears that the new 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.

Just hours after the cease-fire went into effect on October 18, both sides traded accusations of violating the new truce.

A building damaged by recent shelling in Nagorno-Karabkah's main city of Stepanakert on October 17.

Armenian Defense Ministry spokeswoman Shushan Stepanian accused Azerbaijani forces of shelling and carrying out missile strikes in the conflict zone overnight.

“The enemy launched an attack in the southern direction" of the conflict zone, and there were “casualties and wounded on both sides," she said.

Azerbaijan's Defense Ministry maintained that Armenian forces continued shelling in the conflict zone overnight despite the cease-fire and in the morning launched attacks in several directions.

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The ministry also accused Armenia of using large-caliber weapons to attack the positions of the Azerbaijani Army in two regions north of Nagorno-Karabakh along the border between the two countries, a claim Armenian military officials denied.

Meanwhile, authorities in Nagorno-Karabakh said on October 18 that it had recorded another 40 casualties among its forces, pushing the military death toll to 673 since the fighting erupted.

Armenia and Azerbaijan agreed on the new cease-fire late October 17, posting identical statements on their respective Foreign Ministry websites.

The statements said the decision was taken following statements earlier this month from the presidents of France, Russia, and the United States, representing the co-chair countries of the Minsk Group of the Organization for Security and Cooperation in Europe (OSCE).

France, Russia, and the United States comprise the OSCE’s Minsk Group, a diplomatic initiative aimed at trying to resolve the conflict, which dates to 1988 in the waning days of the Soviet Union.

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A cease-fire announced last week was repeatedly violated by both sides not long after it went into effect and had all but collapsed before the new cease-fire was agreed.

Earlier on October 17, a missile hit a residential area in Azerbaijan’s second-largest city, killing 13 people and injuring more than 50, one of the deadliest against civilians to date.

The strike in Ganca, about 100 kilometers north of Nagorno-Karabakh, occurred at around the same time that another missile hit Mingacevir, a city east of Ganca and home to a large hydroelectric dam.

It was also unclear where the missile that hit Ganca was fired from; Ganca is about 100 kilometers east of the border with Armenia proper.

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A missile fired directly from Armenian territory onto an Azerbaijani city would be a major escalation of the conflict.

In a televised address after the missile hit Ganca, Azerbaijani President Ilham Aliyev denounced the strike as a war crime and warned the leadership of Armenia.

“Azerbaijan will give its response and it will do so exclusively on the battlefield,” Aliyev said.

Earlier in the week, Baku and Yerevan each claimed gains in the fighting in and around the territory, which was populated by around 150,000 ethnic Armenians prior to this round of violence.

There has been no confirmed death toll from the latest fighting, but the de facto leadership in Nagorno-Karabakh has reported 633 soldiers killed. Azerbaijan has not released any military casualty figures.

Several dozen civilians had been reported killed prior to the October 17 missile strike.

With reporting by AFP and Interfax