Azerbaijan and Armenia accused each other of violating a new ceasefire to halt fighting over Nagorno-Karabakh, which was due to take effect on Monday.

Azerbaijan's Foreign Ministry said Armenian forces had shelled the town of Terter and nearby villages in "gross violation" of the truce, which was announced by Washington on Sunday and was due to start at 8:00 a.m. local time (0400 GMT).  

Armenia's Defense Ministry said Azerbaijani forces had "grossly violated" the ceasefire with artillery fire on combat positions in various parts of the frontline. 

The U.S. State Department said on Sunday that a humanitarian ceasefire would take effect on Monday in the conflict between Armenia and Azerbaijan over the Nagorno-Karabakh region.

The announcement came after U.S. Secretary of State Mike Pompeo held separate meetings with the foreign ministers of Armenia and Azerbaijan in Washington on Friday.

Those meetings were joined by the co-chairs of the OSCE Minsk Group, formed to mediate the conflict and led by France, Russia and the United States, which described them as "intensive discussions" on the ceasefire and the beginning of talks about core elements of a comprehensive solution. 

The Minsk Group said its co-chairs and the foreign ministers agreed to meet again in Geneva on Thursday. 

"Congratulations to Armenian Prime Minister Nikol Pashinyan and Azerbaijani President Ilham Aliyev, who just agreed to adhere to a cease fire effective at midnight. Many lives will be saved," U.S. President Donald Trump wrote on Twitter. 

Read more: 

A look back at the decades-long conflict over Nagorno-Karabakh region

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But the eruption of new fighting on Sunday and the collapse of two previous ceasefires brokered by Russia raised questions about the prospects for this fresh push to end the clashes. 

The ongoing armed conflict broke out on September 27 along the contact line of the Nagorno-Karabakh region. Armenia and Azerbaijan have been at loggerheads over the mountainous region since 1988. Peace talks have been held since 1994 when a ceasefire was reached, although there have been minor sporadic clashes. 

(With input from agencies)

(Cover: Smoke rises as targets are hit by shelling during the fighting over the Nagorno-Karabakh region near the city of Terter, Azerbaijan, October 23, 2020. /Reuters)