Migrants ask for help from a dinghy as they are approached by the SOS Mediterranee’s ship Aquarius, background, off the coast of the Italian island of Lampedusa, on Sunday. (Patrick Bar/Associated Press)

THE NEWS of the latest human tragedy in the Mediterranean came just as Europe’s leaders were congratulating themselves on having curtailed the flow of desperate refugees attempting to reach their shores. According to the United Nations refu­gee agency, some 500 people may have drowned last week when a large boat jammed with migrants from Africa sank somewhere between Libya and Italy. The survivors, 41 Somalis, Ethiopians, Egyptians and Sudanese, drifted at sea in another boat for several days before being rescued. “All the people died in a matter of minutes,” one told investigators.

European Union officials have been touting the initial success of a strategy to prevent asylum seekers from Syria and elsewhere in the Middle East from crossing the Aegean Sea from Turkey to Greece. The scheme is morally and legally dubious: New arrivals in Greece are being deported back to Turkey in exchange for $6 billion in E.U. aid to the regime of Recep Tayyip Erdogan — and, it seems, pandering to his political demands, including the prosecution of a German comedian who insulted him. The dirty reward is that landings in Greece have dropped off precipitously, from 26,000 in the three weeks before the policy was launched to fewer than 6,000 since April 4.

Nothing has been done to address the causes of the exodus, however, so smugglers might shift their activities from the Turkey-Greece route to the still more dangerous passage between the North African coast and Italy. Some 6,000 mostly African refugees arrived in southern Italian ports in four days last week, according to the International Organization for Migration, bringing the total for the year to nearly 24,000. Some 800 have died along the way, the agency said , including those in the latest accident.

Predictably, some European leaders are calling for more aggressive measures to stop the flow of boats, including stationing European warships in Libyan waters. While some measures of force may be appropriate, what’s missing is a more humanitarian commitment to provide for those seeking refuge and to tackle the conflicts driving them from their homes.

In a statement on the latest sinking, the U.N. refu­gee agency said “increased regular pathways for the admission of refugees and asylum seekers to Europe” was the way to undermine the smugglers. So far, however, most countries are failing to meet E.U. quotas for resettling refugees already in Europe; a number have also failed to pay into a fund to cover the cost of the Turkey deal.

Italian Prime Minister Matteo Renzi has proposed a plan for providing aid to African countries in exchange for more measures to stop people-smuggling. However, this potentially worthy approach quickly became tangled in a debate over funding, with Germany flatly rejecting Mr. Renzi’s suggestion that money be raised through the issuance of Eurobonds.

Meanwhile, no one in Europe appears ready to take the steps that would do most to solve the problem: ending the assaults on civilians by the Syrian regime of Bashar al-Assad, and helping a new, internationally backed Libyan government establish its authority. The Syrian mess is tacitly delegated to the Obama administration, which continues to insist on a failing strategy of leverage-free diplomacy. The result will be more desperate asylum-seekers’ journeys, and more tragedy.