HARARE, Zimbabwe -- Longtime President Robert Mugabe ignored a midday deadline set by the ruling party to step down or face impeachment proceedings, while Zimbabweans stunned by his lack of resignation during a national address vowed more protests to make him leave.

"Arrogant Mugabe disregards Zanu PF," one newspaper headline said.

Zanu-PF, once Mugabe's own party, said Monday that impeachment proceedings were underway, citing Mugabe's disregard for the country's laws which, according to the party, led to the "unprecedented economic tailspin" facing Zimbabwe.

The state-run broadcaster said ruling party members were summoned to a meeting on Monday afternoon as the talk of an impeachment grew louder.

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Opposition activists and the influential liberation war veterans association announced more demonstrations to pressure the 93-year-old Mugabe, the world's oldest head of state, to step down after 37 year in power.

"Your time is up," veterans association leader Chris Mutsvangwa said at a press conference. "You should have the dignity and decency to spare the country of further turmoil by simply announcing your departure immediately."

He also suggested that the military, even though it put Mugabe under house arrest days ago, was still beholden to him and compelled to protect him because he is officially their "commander in chief."

Zimbabweans were astonished that Mugabe, flanked by the military in his national address Sunday night, remained defiant.

The war veterans' association will go to court to argue that Mugabe is "derelict of his executive duty," Mutsvangwa said.

Some ruling party members said an impeachment process likely wouldn't lead to Mugabe's immediate resignation and could take days to complete. Mugabe was stripped of his party leadership on Sunday by the Central Committee of the ruling ZANU-PF but said in his speech he would preside over a party congress next month.

The congress is expected to ratify his firing as party chief, the expulsion of the unpopular first lady and the naming of Mugabe's recently fired deputy to succeed him.

Amid the confusion, some people in the capital, Harare, are now more cautious about talking to reporters. That contrasts with the jubilation and open condemnation of Mugabe over the weekend, when the bulk of Harare's population of roughly 1.6 million appeared to be in the streets, dancing and taking selfies with soldiers in an event backed by the military.

At the University of Zimbabwe on Monday, students protested and refused to sit for exams, singing and demanding that Mugabe step down. The spokesman for the Zimbabwe National Students Union, Zivai Mhetu, said they want all universities shut down until he does.

Mugabe in his speech acknowledged "a whole range of concerns" of Zimbabweans about the chaotic state of the government and its collapsed economy, but he stopped short of what many in the southern African nation were hoping for - a statement that he was stepping down.

The once-formidable Mugabe is now a virtually powerless figure, making his continued incumbency all the more unusual and extending Zimbabwe's political limbo. He is largely confined to his private home by the military.

Yet the president sought to project authority in his speech, which he delivered after shaking hands with security force commanders. The army commander himself, whose threat to "step in" last week led to Mugabe's house arrest, leaned over a couple of times to help the president find his place on the page he was reading.

Mugabe has discussed his possible resignation on two occasions with military commanders after they effectively took over the country on Tuesday. The commanders were troubled by his firing of his longtime deputy and the positioning of unpopular first lady Grace Mugabe to succeed him.

"I, as the president of Zimbabwe, as their commander in chief, do acknowledge the issues they have drawn my attention to, and do believe that these were raised in the spirit of honesty and out of deep and patriotic concern for the stability of our nation and for the welfare of our people," Mugabe said.

The deputy whom Mugabe fired, former Vice President Emmerson Mnangagwa, is positioned to become Zimbabwe's next leader after the party committee made him its nominee to take over from Mugabe, who has ruled since independence from white minority rule in 1980.

The military appears to favor a voluntary resignation to maintain a veneer of legality in the political transition. Mugabe, in turn, is likely using whatever leverage he has left to try to preserve his legacy or even protect himself and his family from possible prosecution.