Harare, Zimbabwe - Crowds of Zimbabweans gathered outside parliament and upped their call for President Robert Mugabe to quit as MPs began a process to impeach the 93-year-old leader.

Parliament received the motion by the ruling ZANU-PF party on Tuesday, heard in a joint sitting of the lower and upper house, accusing Mugabe of being "the source of instability" within government and allowing his wife, First Lady Grace, to "usurp constitutional power".

The opposition Movement for Democractic Change party seconded the motion.

As laid out in Section 97 (3) of the Constitution, once the Senate and National Assembly have passed a resolution confirming the president should be removed from office, Mugabe could be stripped of his wide-ranging powers that many citizens say have caused untold suffering and hardship.

Douglas Gumbo, 54, who participated in Saturday's mass march calling for Mugabe to resign, told Al Jazeera he was eager to watch the parliamentary session. House sittings are normally broadcast live on state television.

"He tried to run away from us on Sunday, but now he is cornered. It's game over for him and I just can't wait to see him and his wife go," he said.

Impeachment requires a two-thirds majority of both the senate and the national assembly.

While the governing ZANU-PF party, which has turned against its leader, holds a parliamentary majority, it may have to team up with opposition legislators to make up the required numbers.

Dozens of ZANU-PF MPs have fled the country or gone into hiding facing army detention, following a military crackdown targeting "criminals" surrounding the veteran leader.

Meanwhile, the Southern African Development Community (SADC) bloc wrapped an extraordinary session on Tuesday, held to discuss the Zimbabwe situation in neighbouring Botswana, where the SADC is headquarters is located.

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

Also on Tuesday, Emmerson Mnangagwa, the vice president Mugabe sacked on November 6, reportedly joined calls for the leader to resign.

"The people of Zimbabwe have spoken with one voice and it is my appeal to President Mugabe that he should take heed of this clarion call and resign forthwith so that the country can move forward and preserve his legacy," he said in a statement that has been circulating around local media.

Mugabe ignores ZANU-PF deadline

A military takeover, launched on November 15, placed Mugabe under house arrest - he is largely confined to his Blue Roof residence.

Despite increasing pressure, Mugabe has resisted demands to resign, instead maintaining "a business as usual" stance, calling for a cabinet meeting ahead of Tuesday's parliamentary session, as is routine.

On Monday, he disregarded an ultimatum from ZANU-PF demanding he submit his written resignation as national president.

In a national address broadcast on Sunday, Mugabe said he would "preside" over the party's upcoming extraordinary congress next month.

Former Zambian President Kenneth Kaunda reportedly jetted in on Monday on an official mission to convince Mugabe to step down in a "dignified exit".

Kaunda is a close ally of Mugabe and like his 93-year-old age mate, was neighbouring Zambia's first president after liberation in 1964.

However, after 27 years, he conceded electoral defeat and stepped down.

If Mugabe's impeachment sails through it could see Mnangagwa, the sacked vice presient, appointed as interim president.

Mnangagwa, who fled Zimbabwe after being dismissed on November 6 amid a power to struggle with Grace Mugabe, was reinstated as ZANU-PF's vice president and appointed interim party leader.

According to army chief General Constantino Chiwenga, Mnangagwa - Mugabe's longtime heir apparent, is expected back in the country "shortly".

Follow Tendai Marima on Twitter: @i_amten