The European Union is promising to act quickly in response to new tactics of smugglers bringing migrants across the Mediterranean to Europe packed aboard huge, decaying cargo ships.

European Commission spokesman Margaritis Schinas said Monday that "we have to act and we shall act swiftly."

The EU Frontex border agency says about 15 such crossings have been recorded since August. Two came in just three days last week, involving more than 1,000 migrants, many of them fleeing Syria.

Schinas said that even though Frontex vessels were involved in last week's rescue efforts the EU could be doing more.

He said that would require EU countries to provide "more means, more instruments, more money."