An explosion has disrupted a huge rally for Ethiopia’s new, reformist prime minister shortly after he addressed a huge crowd.

Abiy Ahmed described the explosion as a “well-orchestrated attack” but one that failed. It happened when he was waving to one of the biggest crowds to gather in the east African nation in recent years.

In an address to the nation shortly after the blast, Abiy said some people had been killed and others injured. He has not blamed anyone for the blast, which he called “cheap and unacceptable”. Police are investigating.

The prime minister said: “Love always wins. Killing others is a defeat. To those who tried to divide us, I want to tell you that you have not succeeded.”

Tens of thousands of Ethiopians heartened by a wave of reforms under Abiy had packed Meskel Square in a show of support.

Footage showed the prime minister being rushed from the scene by security guards.

Abiy had addressed the crowd as supporters wore clothes displaying his image and carried signs saying “One Love, One Ethiopia”. He told them 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 more reforms.

Abiy, 42, took office in April and surprised Africa’s second most populous country by announcing the release of tens of thousands of prisoners, the opening of state-owned companies to private investment and the unconditional embrace of a peace deal with rival Eritrea.

The US is among those expressing support for the changes in a key security ally.

But not everyone has welcomed the changes. Some Ethiopians near the border with Eritrea have protested against the peace deal. And the Tigrayan People’s Liberation Front, a party in Ethiopia’s ruling coalition that has been the dominant force in government for most of the past 27 years, said the announcement on the peace deal had been made before the ruling coalition’s congress met to discuss it.