YEREVAN (Reuters) - Armenian Prime Minister Nikol Pashinyan’s grip on power appeared to be slipping on Friday, a day after the army called on him to quit. Hundreds of demonstrators rallied in the capital Yerevan to demand his downfall, and a leading opposition figure called on the army to rebel against him. Two former presidents have already said he must step down. Pashinyan, 45, accused the military of a coup attempt on Thursday and tried to sack the chief of staff, after the army issued a written statement calling for him to resign. He has faced calls to quit since November from countrymen who blame him for a disastrous six-week war that saw ethnic Armenian forces lose swathes of territory in neighbouring Azerbaijan they had held for decades. While crowds on Friday demanded he resign, thousands of others had gathered in the capital to rally behind him on Thursday. Pashinyan told his supporters on Thursday he was firing Onik Gasparyan, the chief of the army’s general staff. But by Friday the dismissal had not yet been approved by Armenia’s president, a step needed for it to enter force. President Armen Sarkissian held a meeting with Gasparyan, the president’s office said, without releasing further details. Vazgen Manukyan, a politician who has been touted by the opposition as a possible interim prime minister to replace Pashinyan, told hundreds of supporters at a rally that the army would never allow Gasparyan to be sacked. “You think the army will easily agree that Pashinyan illegally removes their head? No. The army will rebel. I call on the army to rebel. The army shouldn’t carry out illegal orders,” Manukyan said. The General Prosecutor’s Office told Reuters on Friday that it was investigating whether the army’s call for the prime minister to go constituted a crime. “The general staff’s statement and the possible risk of developments around it are the subject of our attention,” Gor Abrahamyan, an aide to the prosecutor general, told Reuters by telephone. “If any elements of a crime outlined in the criminal code are revealed, a legal response will immediately follow.” Pashinyan, a former journalist and lawmaker, came to power in a peaceful popular uprising in May 2018 known as Armenia’s velvet revolution. But the loss of territory in and around the enclave of Nagorno-Karabakh last year was a bitter blow for Armenians, who had won control of the area in the 1990s in a war which killed at least 30,000 people. The conflict was brought to a halt by a ceasefire deal brokered by Russia. Moscow, which has deployed peacekeepers to enforce the ceasefire, said on Friday it was vital the agreements be fully implemented despite Armenia’s crisis.