The activists are demanding that the drastic humanitarian situation in Zimbabwe is addressed at the summit, which opened on Sunday in Addis Ababa.
An online petition, signed by more than 1,200 people, is to be presented to African heads of state at the summit to urging that pressure be applied to Zimbabwe to free political prisoners and restore basic freedoms.
The summit is ostensively being held to address the development of transport and energy systems on the continent.
However, it comes a day after the AU adopted a resolution calling for Western countries to lift sanctions against Zimbabwe and take steps "to help ease the humanitarian situation in the country".
"I think that everybody today should help Zimbabwe to rebuild its economy, because an agreement has been reached," Jean Ping, the African Union head, said on Saturday.
The AU asked all members and partners "to solidly back the implementation of a comprehensive pact" to end the political deadlock in the country.
Zimbabwe’s Movement for Democratic Change (MDC) has agreed to join a unity government led by Robert Mugabe, the country’s president, putting into effect a power-sharing deal under which, Morgan Tsvangirai, the MDC leader, would become prime minister.
Regional politicians, who have been brokering a compromise between the Zimbabwean rivals, are pressing for the unity government to be formed by February 13.
The country has been in political limbo since disputed polls held last March. The economy has deteriorated to the point that most Zimbabweans cannot buy food and a cholera epidemic broke out last August.
The European Union last week tightened sanctions on Harare by adding more than 60 Mugabe allies and companies to an assets freeze that bans them from travelling to, or trading with, EU nations.
Sheikh Sharif Sheikh Ahmed, Somalia’s new president, attended the summit in Addis Ababa a day after gaining power.
He has asserted his desire to bring the Horn of Africa country – where 3,500 AU peacekeepers are stationed – back into the regional fold.
Recent instability in Madagascar also led the AU’s Ping to warn on Saturday that "any unconstitutional change of power will be condemned".
About 20 leaders from the AU’s 53 members attended the summit on Sunday.
Talks focused on whether the grouping should evolve into an EU-style system for regional governance.
Muammar Gaddafi, Libya’s leader, is heading calls for a union government to augment Africa’s international standing.
However, many of his counterparts are against relinquishing any sovereignty.
It was indicated by delegates that there was little progress made on the issue during the session.