Like so many other groups around the world, the African Union has condemned Donald Trump’s controversial immigration ban, calling it “one of the greatest challenges to our unity and solidarity."

The comments were made during the 28th annual AU summit Monday in Addis Ababa, where 53 leaders representing member states discussed the union’s new leadership; however, many also took the opportunity to express their concerns about Trump’s temporary travel on seven Muslim-majority countries, three of which are a part of the AU.

“The very country to which many of our people were taken as slaves during the transatlantic slave trade has now decided to ban refugees from some of our countries,” said AU President Nkosazana Dlamini-Zuma, according to the Independent.

UN Secretary General Antonio Guterres also spoke at the summit, reminding attendees that African nations have a record of embracing those who are fleeing from violent areas.

“African nations are among the world's largest and most generous hosts of refugees," Guterres said. "African borders remain open for those in need of protection when so many borders are being closed, even in the most developed countries in the world."

On Friday, the president signed an executive order that bans travel from seven Muslim nations. Three of those nations are AU member states—Libya, Somalia, and Sudan; the other four are Syria, Iraq, Yemen and Iran. In the days following the ban, tens of thousands of protestors have condemned the order for discriminating against Muslims. Former President Barack Obama has also criticized the travel ban, while expressing support of the nationwide protests.

“President Obama is heartened by the level of engagement taking place in communities around the country," a statement from Obama spokesperson Kevin Lewis read. "In his final official speech as President, he spoke about the important role of citizen and how all Americans have a responsibility to be the guardians of our democracy—not just during an election but every day."