Merkel's surprise summit took place after Sunday's EU-Turkey summit, in which Turkey's long-time EU membership bid was revived alongside an EU pledge of some 3 billion euros ($3.2 billion) to Ankara intended to assist Syrian refugees in Turkey.
With plans for mandatory migrant quotas upset by strong opposition from some EU member states, Merkel has turned to a nine-country "coalition of the willing" to increase refugee intake voluntarily.
"This is a meeting of those states which are prepared to take in large numbers of refugees from Turkey legally," European Commission President Jean-Claude Juncker said, according to The Guardian newspaper.
"Let us not be naive. Turkey is not the only key to solving the migration crisis," European Council President Donald Tusk said, adding that EU border control was necessary to preserve the Schengen free-travel zone.
The International Organization for Migration (IOM) has estimated that over 840,000 migrants arrived to Europe through the Mediterranean, mostly via Turkey, in 2015. Merkel's coalition of the willing could distribute 400,000 refugees among members, according to reports.