LUXEMBOURG—The European Union pledged a set of measures aimed at stepping up its response to a growing migration crisis and stemming the thousands of people risking the dangerous sea crossing to Europe.

The proposals, which now go to EU leaders for approval at an emergency summit on Thursday, include greater resources and a broader mandate for a joint EU-Italian border-control mission, as well as a possible military operation to destroy boats used by people smugglers.

The efforts mark the European bloc’s first concrete steps in months toward developing a more cohesive plan of action to grapple with the humanitarian emergency. The crisis has spiraled as growing numbers of migrants from Africa and the Middle East seek to escape strife and economic turmoil via Libya, whose collapse has allowed human-smuggling rings to flourish along its coast.

Still, many of the proposals lacked specifics, while others have been tried—and failed—in the past. The centerpiece of the plan, bolstering the control-and-rescue mission, known as Triton—would likely remain less ambitious than the Italian-led search-and-rescue operation that preceded it.

The moves comes a day after what is shaping up to be one of the most deadly disasters on the Mediterranean. As many as 700 migrants are believed to have died when an overcrowded boat capsized near the Libyan coast over the weekend.