One person was killed and scores were injured on Saturday in a grenade explosion at a rally for Ethiopia's new reformist Prime Minister Abiy Ahmed attended by thousands in Addis Ababa.
The rally was being held in Ethiopia's capital in support of the 41-year-old ex-soldier who has outlined a series of radical reforms since taking office in April.
Health Minister Amir Aman said on Twitter that 154 people were injured and another had died, without giving further details.
"Some whose heart is filled with hate attempted a grenade attack," the prime minister's chief of staff Fitsum Arega wrote on Twitter, vowing that the perpetrators will be brought to justice.
Six suspects are being held over the attack, said police later on Saturday.
Abiy described the incident as "an unsuccessful attempt by forces who do not want to see Ethiopia united."
He spoke in a televised address following the explosion, which occurred minutes after he finished his speech at the rally.
The rally began as a show of exuberance, with supporters wearing clothes displaying Abiy's image and carrying signs saying "One Love, One Ethiopia."
In a cowboy hat and T-shirt, Abiy told the tens of thousands of supporters that change was coming and there was no turning back.
"For the past 100 years hate has done a great deal of damage to us," he said, stressing the need for even more reforms.
After the explosion the state broadcaster quickly cut away from coverage of the rally, which broke up with people singing, chanting and going back to their homes.
Abiy stunned Ethiopians this month by saying he was prepared to fully implement a peace deal with Eritrea signed in 2000 and meant to end a two-year war between the country and its neighbor that devolved into a stalemate resulting in huge military build up by both countries.
It is one of many policy shifts announced since Abiy took office, moves that could reshape Ethiopia’s relations with its neighbors and have equally dramatic impacts inside the country of 100 million people.