Robert Mugabe has attended a university graduation ceremony on the outskirts of Harare in his first public appearance since a takeover by the Zimbabwean military on Wednesday.

Clad in academic gown and hat, the 93-year-old walked slowly in a procession on a red carpet to a podium as a marching band played. He was applauded as he announced the opening of the ceremony.

His appearance followed an army statement, broadcast on national television and published by state-run media on Friday morning, that appears to have been aimed at quelling growing concerns that the military takeover could swiftly descend into chaos.

Mugabe has resisted pressure to step down and the army is facing growing calls to outline its plans for a new government.

The statement said the army had made significant progress and had “accounted for some of the criminals around [Mugabe] in order to bring them to justice since they were committing crimes that are causing social and economic suffering in the country while others are still at large”.

Since taking power, the military has arrested around a dozen senior officials and leading members of the G40, a faction of the ruling Zanu-PF party who are loyal to Grace Mugabe, the president’s wife.

The takeover is thought to have been prompted in part by fears among the military and its allies within the ruling party of an imminent purge of rivals of the first lady which would allow her to exercise greater power.

Images released by the army on Thursday evening showed Mugabe, 93, meeting the general who led the takeover.

Mugabe, who has ruled Zimbabwe for 37 years, looked relaxed and healthy in the images, taken during a meeting at the president’s state offices and residence in Harare on Thursday afternoon. The defence minister and two South African envoys also appeared in the pictures.

One picture showed Mugabe and General Constantino Chiwenga, the head of the armed forces, smiling as they shook hands. No details of the conversations held during the meeting were released.

Friday’s statement from the military respectfully referred to Mugabe as “commander in chief”. However there are signs that the patience of the military and its supporters within Zanu-PF is growing thin.

Leaders of the party are meeting on Friday to draft a resolution to dismiss Mugabe at the weekend and lay the ground for his impeachment next week if he refuses to stand down, a senior party source told Reuters.

“There is no going back,” the source said. “If he becomes stubborn, we will arrange for him to be fired on Sunday. When that is done, it’s impeachment on Tuesday.

A march of members and associations is being organised by Zanu-PF leaders for Saturday to call for Mugabe to step down.

Until Friday’s appearance at the graduation ceremony Mugabe had been confined to his personal residence in the capital’s upscale neighbourhood of Borrowdale since Tuesday, when troops seized the state TV channel’s studios and other important sites.

Sources close to the military said Mugabe had described the takeover as illegal. He is thought to have rejected efforts by a Catholic priest – a long-term friend – to facilitate mediation talks.

South African envoys are in Harare to help with negotiations and decide the terms of Mugabe’s resignation. South Africa, the biggest regional power, called an emergency meeting of the Southern African Development Community regional bloc, in Botswana. The meeting was inconclusive, though a final statement condemned changes of government through unconstitutional means.

The military move has been cautiously welcomed by many Zimbabweans and the streets were quiet again on Friday, but there are growing public demands for those who led the takeover to lay out their plans.

The army has said the takeover was a temporary measure to “target criminals” around Mugabe, resolving a succession battle that has pitted Grace Mugabe against the former vice-president Emmerson Mnangagwa.

Mnangagwa was reported to have returned to Zimbabwe on Tuesday evening from South Africa, where he fled last week after being stripped of his office by the president in an apparent attempt to clear Grace Mugabe’s path to power.