President Robert Mugabe is fast losing his grip on the country and pressure is building on him to quit. Here's what you need to know:

What is happening?

Mugabe, 93, has ruled Zimbabwe for 37 years and many claim his leadership has been repressive. He heads the ZANU-PF party and is the world's oldest head of state.

In a dramatic turn, the army placed Mugabe under house arrest on November 15 and there are now increasing calls for him to quit.

On Saturday, thousands gathered in the capital Harare and the second city of Bulawayo to demand Mugabe's resignation in scenes that would have been unthinkable one week ago.

On Sunday, ZANU-PF expelled him as leader and gave him a Monday noon deadline to resign, or face impeachment.

In a national address later on Sunday, Mugabe defied widespread calls to quit, pledging to preside over a ZANU-PF congress next month.

Why did the army target Mugabe?

The army insists it is not launching a coup, but on November 15, as well as placing Mugabe under house arrest, the military seized the state broadcaster and blocked access to government sites.

The takeover unfolded after Mugabe sacked Vice President Emmerson Mnangagwa on November 6 for showing "traits of disloyalty".

The ex-vice president is an ally of army chief General Constantino Chiwenga and a veteran of the country's struggle for independence.

Many believe Mugabe sacked Mnangagwa to make way for his wife Grace to become vice president and eventually rule the country.

Army commander Chiwenga had warned that the military would act if purges against former war liberation fighters did not cease.

Who are the war veterans?

War veterans, who fought alongside Mugabe during the 1970s struggle for liberation from Britain and spearheaded the repossession of white-owned commercial farms in the 2000s, claim their president has betrayed the revolution.

The ongoing purges of scores of Mnangagwa allies have widened the rift between the Mugabes and various groups of war veteran leaders.

Victor Matemadanda, secretary-general of the Zimbabwe National War Veterans Association, recently told Al Jazeera the ongoing expulsions were a strong indication that Mugabe was acting in his own interests and those of his wife.

Who's with Mugabe and who is against him now?

As well as the army, opposition and war veterans, some members of Mugabe's own party have turned against him. All 10 of ZANU-PF's provincial structures have passed a motion of no-confidence against Mugabe and called on him to step down as the ruling party's first secretary.

On Sunday, regional dignitaries from the Southern African Development Community (SADC) were expected to meet in an extraordinary session to discuss the Zimbabwe situation in neighbouring Botswana, where the SADC headquarters is located.

SADC chair, South African President Jacob Zuma, is a close ally of Mugabe and was the first to talk to the leader after the military takeover.

While the region's leaders have been silent on Mugabe's fate, Botswana's President Ian Khama has openly called for the elderly president to step down.

Will Mugabe quit?

He has certainly lost his grip on power, but whether he will resign remains to be seen.

Mugabe made his first public appearance on Friday, two days after being placed under house arrest, as he attended a graduation ceremony.

In his televised address on Sunday, Mugabe vowed to preside over ZANU-PF's key party conference in December, despite having been dismissed as leader of the party.

"The party congress is due in a few weeks and I will preside over its processes," said Mugabe.

Analysts, however, say the end of his decades-long rule is near.

"I'll be most surprised if he survives the week," Stephen Chan, professor and author of Robert Mugabe: A Life of Power and Violence, told Al Jazeera on Sunday.

"He can't address the Congress; he is no longer the president of the party.

"This is just defiance - this is simply the old man going down with all of his guns firing. They are blank shots, however, because they can't have any real effect."