Nine police officials, including the deputy head of the Addis Ababa police commission, have been arrested over alleged security lapses.
“Ethiopian police have confirmed that nine policemen have been arrested because of what they are calling gross negligence; for not putting enough security measures in place to make sure that such an incident did not occur,” said Al Jazeera’s Mohammed Adow reporting from Addis Ababa.
Six other suspects are also being held over links to the attack, but no group has claimed responsibility for the blast.
In an address broadcast afterwards on state television, Abiy said the blast was orchestrated by groups who wanted to undermine the rally but did not name them.
“The people who did this are anti-peace forces. You need to stop doing this. You weren’t successful in the past and you won’t be successful in the future.”
The blast has sent shockwaves across the country as the new prime minister, who enjoys a lot of political support, especially among the younger generation, seeks to enforce his reformist agenda.
Since assuming office in April, Abiy has introduced a number of reforms and has overseen the release of jailed dissidents and moved to liberalise the economy.
He has also made peace overtures with aggrieved opposition groups, as well as neighbouring Eritrea.
“Abiy’s effort to move the country forward has angered those who for a very long time maintained a stronghold on the country’s politics and economy,” Mohammed Ademo, political commentator and founder of OPride.com, an independent news website on Ethiopia, told Al Jazeera.
“They are trying to scare people and undermine the prime minister so they can send a signal that he is not capable of stabilising the country,” Ademo added.
“Many Ethiopians are shocked that people would go to such lengths to stop what they see as a really positive move – the reforms they say this country really needs,” said Al Jazeera’s Adow.
Ethiopia was rocked by mass anti-government protests in 2015, which first broke out in the populous Oromia region, home to the Oromo, after the unveiling of plans for a controversial development project in Addis Ababa.
The rallies then spread to other parts of Ethiopia, including the Amhara region, with demonstrators demanding an end to human rights abuses as well as political reforms and greater freedoms.
Hundreds of people were killed and more than 20,000 others were arrested in a government crackdown that was widely condemned by human rights organisations.
SOURCE: AL JAZEERA AND NEWS AGENCIES