ADDIS ABABA - The death toll from a grenade attack on a pro-government rally in Ethiopia's capital climbed to two on Sunday, a cabinet minister said, as police announced arrests over the blast. "I'm so sorry to learn that we have lost another Ethiopian victim of yesterday's attack," health minister Amir Aman tweeted. "My sincere sympathy and condolences to the family, friends and all Ethiopians." The blast occurred in a packed public square as Ethiopia's new prime minister Abiy Ahmed was wrapping up a speech before tens of thousands of people.

The ensuing chaos injured more than 150 people and marred an event meant to build public support for Abiy's ambitious reform agenda. State-run Ethiopian News Agency reported police had arrested six people suspected of involvement in the blast, but gave few details.

Event organiser Seyoum Teshome on Saturday told AFP police grappled with someone attempting to hurl a grenade at the prime minister as he concluded his speech.

The explosive detonated amid the scuffle, though most of the injuries were caused in the ensuing panic, he said.

On Saturday evening, the prime minister visited hospitals where victims of the attack were being treated, his chief of staff said on Twitter, while on Sunday one of Addis Ababa's largest football teams organised a blood drive for the injured.

No group has publicly claimed responsibility for the attack, a rare instance of violence in the heavily policed capital.

Grenade attacks were reported last year in the northern city of Gondar, but it was unclear if those incidents were connected to Saturday's blast.

Abiy took office in April after years of anti-government unrest that pushed his predecessor to resign and the government to declare a nationwide state of emergency.

He has since announced plans to liberalise the economy and reconcile with neighbouring arch-enemy Eritrea.

Abiy also lifted the state of emergency and released scores of jailed dissidents.

Ethiopia is completely controlled by the secretive Ethiopia People's Revolutionary Democratic Front (EPRDF), and it is unclear how much support Abiy has within the party.

The 42-year-old former government minister and army officer is the first prime minister in modern Ethiopia from the country's largest ethnicity the Oromo, which spearheaded the anti-government protests.

While Abiy is popular, anti-government fervour still remains.

After the prime minister's hasty departure following the blast, people swarmed the stage where he had spoken and chanted "down down Woyane," an anti-government slogan aimed at the Tigrayan ethnic minority many Ethiopians believe dominates the EPRDF.