Armenia and Azerbaijan have agreed to a new US-brokered ceasefire in the disputed territory of Nagorno-Karabakh.

However, both sides accused each other of violating the agreement minutes after it came into effect at 08:00 local time (04:00 GMT) on Monday.

The agreement was reached following intense negotiations, the US state department said.

Two other ceasefires agreed earlier this month over the conflict were broken almost immediately.

Fighting erupted on 27 September around the mountainous enclave. The conflict has intensified again in recent days.

Armenia and Azerbaijan agree to US-brokered ceasefirehttps://t.co/DFQl2qWifE

— BBC News (World) (@BBCWorld) October 25, 2020

The "humanitarian ceasefire" was announced on Sunday in a joint statement released by the US, Armenian and Azerbaijani governments.

The announcement followed discussions between US Deputy Secretary of State Stephen Biegun, Armenian Foreign Minister Zohrab Mnatsakanyan and his Azerbaijani counterpart Jeyhun Bayramov.

On Friday, both foreign ministers were in Washington for meetings with US Secretary of State Mike Pompeo.

US President Donald Trump tweeted on Sunday to congratulate those involved.

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. Proud of my team @SecPompeo & Steve Biegun & @WHNSC for getting the deal done!

— Donald J. Trump (@realDonaldTrump) October 25, 2020

However, within minutes of the ceasefire coming into effect, Azerbaijan accused Armenian forces of shelling the town of Terter and nearby villages in "gross violation" of the agreement.

Armenia's defence ministry said Azerbaijani artillery had fired on military positions in various parts of the front line after the ceasefire agreement had begun.

In a post on Facebook, Armenian President Nikol Pashinyan insisted his country "continues to strictly adhere to the ceasefire regime".

Hikmet Hajiyev, a spokesman for the Azerbaijani president, said Armenia was trying to "preserve the status quo based on occupation", adding: "The Azerbaijani side is exercising restraint."

Mediators from the Organization for Security and Co-operation in Europe (OSCE) are also due to meet again on Thursday to discuss the conflict.

Two earlier ceasefires brokered by Russia have failed to hold. The president of Azerbaijan, Ilham Aliyev, has also warned Russia not to get involved militarily in the conflict.

Nagorno-Karabakh is recognised internationally as part of Azerbaijan but is under ethnic Armenian control.

Clashes that began in the region in September quickly escalated into a large-scale conflict, with the shelling of towns and cities and the alleged use of banned cluster munitions.

Several thousand people have died and shelling has killed civilians on both sides. Tens of thousands have fled their homes.