The scandal surrounding slave trading in Libya has overshadowed this EU-Africa summit in Abidjan, Ivory Coast.
Leaders agreed a deal promising to step up voluntary returns and resettlement of those in need.
The announcement comes after pictures emerged of migrants being sold at slave auctions in the North Africa country.
“Let me repeat my call to impose UN sanctions on human smugglers and traffickers,” said European Council president Donald Tusk.
But NGO Doctors Without Borders slammed the EU as being partly responsible on Thursday.
The organisation’s director said EU funding for the Libyan government’s migration policy made it complicit in the treatment of refugees there.
All governments say they want to crack down on the people smugglers.
“We decided on the occasion of this meeting to make sure that the AU and the UN put in place a mechanism that could allow to indwell the networks of the smugglers, to punish the smugglers, to punish the smugglers because this is a crime against humanity,” said Mahamadou Issoufou of Niger.
Euronews correspondent Isabel Marques da Silva reports that leaders have been quick to condemn the conditions in Libyan camps, but she points out that “the chaotic political situation” in Libya will demand a much more detailed strategy from world powers.