"We call on the government of Zimbabwe immediately to cease the state-sponsored violence and intimidation against its people that has occurred since the March 29 presidential and parliamentary election."
The summit draft further said that a "free and fair presidential run-off is critical to the resolution of the ongoing crisis".
Separately, Human Rights Watch (HRW) has said that supporters of Robert Mugabe, the Zimbabwe president, had led a campaign that eliminates any chance of a fair presidential run-off election on June 27.
The US-based organisation said on Monday that it has documented at least 36 politically motivated murders and 2,000 victims of a campaign of killings, abductions, beatings and torture by Mugabe's ruling Zanu-PF party.
The HRW report said more than 3,000 people have fled the violence, which began after the March 29 elections in which Zanu-PF lost control of parliament for the first time.
It said Mugabe's government had incited and perpetrated the violence to intimidate and punish opposition supporters.
It also said that the government had failed to prosecute those responsible, including members of the security forces, liberation war veterans and youth groups.
Official results showed that Morgan Tsvangirai, leader of the opposition MDC party, fell short of the absolute majority needed for outright victory, necessitating the run-off.
Despite the criticism, the Mugabe government says it will only allow election monitors from friendly countries.