The party that Robert Mugabe headed for nearly four decades, on Sunday, dismissed him as its leader in what is another blow to the longtime Zimbabwean president, whom the military detained last week.

The party also told Mugabe that he must resign by noon Monday or face impeachment proceedings.

The actions, unimaginable only a week ago, add to the groundswell of support aimed at ejecting the world’s oldest head of state. But they do not have any immediate effect on Mugabe’s position as president.

On Sunday, Mugabe left his home for the presidential office, where he met with the military commanders who seized control of the government. In a picture released by the state-owned newspaper, one of them saluted Mugabe while the president stood behind his desk, one of many signs that Zimbabwe was hardly undergoing a textbook coup.

Mugabe was also set to address the nation, the state broadcaster said Sunday.

Even as calls for his resignation surged among his critics, the 93-year-old appeared to be resisting, making the road to his dismissal murky and potentially much longer than many Zimbabweans would like.

Still, the fact that those who turned against Mugabe were able to take control of party headquarters and cast a vote against him is telling. After 37 years in power, Mugabe is now technically a leader without a party, his closest allies having been detained by the military.

The central committee of ZANU-PF, the ruling party, voted to replace Mugabe with former vice president Emmerson Mnangagwa and expelled Mugabe’s once-powerful wife, Grace, from its ranks. The committee was composed of Mugabe’s rivals, some of whom had been forced from ZANU-PF months or years ago.

Several Zimbabwean constitutional lawyers said the decision had little bearing on Mugabe’s role as head of state. The party leaders have control only over their ranks and cannot influence the composition of Zimbabwe’s government.

“The party cannot recall him as president, so the legal effect of the vote is limited,” said Fadzayi Mahere, a lawyer and politician. “It’s mostly a political statement.”

Impeachment proceedings could begin Monday, but if Zimbabwean law is followed, it would probably take weeks to unseat Mugabe.

“This is not instant coffee,” said Tendai Biti, a lawyer and opposition member, suggesting that the process could take three weeks. “We can’t sacrifice our constitution to get what we want.”

War veterans leader Christopher Mutsvanga, left, attends an emergency meeting Sunday of the central committee for the nation’s ruling ZANU-PF. (Aaron Ufumeli /EPA-EFE/REX/Shutterstock)

Negotiations between Mugabe and the country’s top military commanders remained the most plausible path to his exit. After detaining the president and arresting his allies Tuesday night, the Zimbabwean military seems unwilling to force Mugabe from power and is attempting a diplomatic approach that would imbue its takeover with an aura of legitimacy.

“If the military had run roughshod, it would have lost the support of the people,” Mahere said.

Instead, Zimbabweans have united behind the military’s actions, an unpredictable turn of events in a country where security forces have for years cracked down on political dissent. On Saturday, a diverse array of opposition groups marched through Harare, the capital, in a buoyant demonstration against Mugabe that felt like a citywide party celebrating his possible ouster.

Across the city, soldiers in armored personnel carriers observed the demonstrations, not intervening and, at times, posing for selfies. They were greeted and praised.

By the time the march was over, the signs for Robert Mugabe Road had been trampled. In front of the party headquarters in downtown Harare, a billboard bearing Mugabe’s face had been vandalized, a hole sliced through the center.

The rally had the air of collective catharsis. For decades, Mugabe had targeted a broad array of his own citizens: farmers from the white minority whose land was seized; political activists who were arrested or simply vanished; even Harare’s street vendors, whom Mugabe has tried to evict.

“This is time for us to make a declaration of what we want, a Zimbabwe in which we have opportunities,” said Evan Mawarire, a pastor and leading activist.

[Zimbabwe seized white farmers’ land. Now some are being invited back.]