Pashinyan had come under pressure in recent days, with thousands of demonstrators protesting since Tuesday and demanding him step down over a cease-fire that secured territorial advances for Azerbaijan in the disputed region Nagorno-Karabakh after six weeks of intense fighting, according to aljazeera.com.
In a statement on Saturday, the NSS said its former head, Artur Vanetsyan, the former head of the Republican Party parliamentary faction Vahram Baghdasaryan and war volunteer Ashot Minasyan were under arrest.
“The suspects were planning to illegally usurp power by murdering the prime minister and there were already potential candidates being discussed to replace him,” the NSS added.
Pashinyan said earlier this week that he had no choice but to sign the Russia-brokered deal to prevent further territorial losses. He said he was taking personal responsibility for the setbacks, but rejected calls to resign.
He described the deal as “painful”, saying, the signing of the agreement was aimed at saving the lives of “25,000 soldiers”, according to armenpress.am.
The cease-fire halted military action in and around Nagorno-Karabakh, an enclave internationally recognized as part of Azerbaijan but populated by ethnic Armenians.
On Saturday, ethnic Armenian villagers in Nagorno-Karabakh set their houses on fire before fleeing to Armenia on the eve of a deadline that will see parts of the territory handed over to Azerbaijan as part of the cease-fire agreement.
Under the agreement, 2,000 Russian peacekeeping troops are being deployed to the region.
Since the early 1990s, ethnic Armenians had held military control over all of Nagorno-Karabakh and substantial swathes of Azerbaijani territory surrounding it. They have now lost much of the enclave itself as well as the surrounding territory.
Armenia announced on Saturday that 2,317 servicemen were killed in the conflict, which forced thousands to flee their homes. Azerbaijan has not disclosed its military casualties.