Ethiopia's new Prime Minister Abiy Ahmed and Zimbabwe's President Emmerson Mnangagwa escaped attacks on their respective rallies in their countries, officials and witnesses said.
In Addis Ababa, the grenade attack was launched by an unidentified assailant moments after 41-year-old prime minister, a former soldier who took office in April, finished his speech to tens of thousands of people gathered in the centre of the capital.
A witness saw Abiy whisked away by guards. Another witness told Reuters the assailant with the grenade had been wrestled to the ground by police before it exploded.
Health Minister Amir Aman said one person was killed and 154 were wounded, with 10 of them in critical condition.
Addressing the nation on television shortly after the blast and still wearing a green t-shirt he was handed at the rally, Abiy said the attack was an "attempt by forces who do not want to see Ethiopia united."
Eritrea, which has long been at loggerheads with Ethiopia over a border row that Abiy has sought to resolve, condemned the incident, as did the European Union and the United States.
In Bulawayo, Zimbabwe's second largest city, President Mnangagwa survived a blast at a ruling ZANU-PF party rally yesterday, his spokesman said, adding that he had been taken to safety after the incident.
An AFP correspondent at the scene reported multiple injuries but could not immediately give a precise toll.
Mnangagwa had been in the city to campaign for votes ahead of nationwide elections due on July 30. They are the first polls since veteran leader Robert Mugabe was ousted following a brief military takeover in November last year, after 37 years in power.