Armenian Foreign Minister Zohrab Mnatsakanyan resigned from his post on Monday, the ministry's spokeswoman wrote on Facebook. 

Mnatsakanyan's resignation came a week after an agreement on a cessation of hostilities in the Nagorno-Karabakh conflict zone, announced in a joint statement by the president of Azerbaijan, the prime minister of Armenia and the president of the Russian Federation. 

Mnatsakanyan had held the position since May 2018. 

The government of Prime Minister Nikol Pashinyan has come under pressure with thousands of demonstrators last week demanding he resign over the ceasefire that secured territorial advances for Azerbaijan in Nagorno-Karabakh after six weeks of fighting. 

After the deal was announced, protesters took to the streets of the Armenian capital Yerevan, calling Pashinyan a "traitor." They also stormed government buildings. 

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On Monday, Pashinyan appealed for calm. "Today I clearly stated that violence or the provoking of violence (especially armed violence) cannot in any way be a means of action for the government," he said on Facebook.  

Pashinyan said he expected the opposition to also declare that it did not back "any violent action."  

Authorities on Saturday said they thwarted a plot to assassinate the prime minister and arrested opposition leader Artur Vanetsyan, the former head of Armenia's security services.  

Vanetsyan, leader of the center-right "Homeland" party, was released on Sunday after a court ruled that his detention lacked legal grounds.   

A dozen opposition leaders were detained last week for inciting riots but were also released by courts. 

(With input from Reuters, AFP)