Several people have been killed and injured in an explosion at a rally attended by thousands in Ethiopia’s capital Addis Ababa.

The blast occurred on Saturday after new Prime Minister Abiy Ahmed concluded addressing the crowd in the heart of the city.

In a televised address following the attack, the 41-year-old ex-soldier described the deadly blast as “an unsuccessful attempt by forces who do not want to see Ethiopia united.”

He said “a few people” were killed and injured as the result of the explosion, but the exact casualty figure is not known yet.

Since coming into office in April, Ahmed has carried out a series of radical reforms in Africa’s second-most populous country, including releasing imprisoned dissidents and acting to liberalize the nation’s economy.

Ahmed succeeded Hailemariam Desalegn, who resigned in February amid a wave of anti-government protests led by the country’s two largest ethnicities.

According to local press reports, he is the country’s first leader from the ethnic Oromo group, which has been at the center of nearly three years of anti-government rallies against persisting marginalization that have left hundreds of people killed.

The Ethiopian government is accused of human rights violations, including torture and extrajudicial killing of political dissidents.