EU foreign affairs chief Federica Mogherini told European nations Monday they had "no more excuses" not to act on the migrant crisis as another boat with 300 people onboard issued a distress call from the Mediterranean.
A day after a fishing boat crammed with migrants capsized off Libya with the loss of hundreds of lives, EU foreign and interior ministers met in Luxembourg to discuss the flood of people desperately trying to reach Europe.
More than 700 people are feared dead in Sunday's disaster, with some survivors suggesting nearly 1,000 could have been on board.
As the search for victims continued, the International Organization for Migration said it had received a distress call from another boat in the Mediterranean.
"The caller said that there are over 300 people on his boat and it is already sinking (and) he has already reported fatalities, 20 at least," the IOM's Federico Soda wrote in an email.
His colleague Flavio Di Giacomo urged caution, however.
"For now, this is simply a call for help... It's too soon to talk about a shipwreck," he told RaiNews24.
Soda said the IOM had given the Italian coast guard the coordinates for the boat and two other stricken vessels, but that rescuers were still busy responding to Sunday's disaster.
Arriving at the talks in Luxembourg, Mogherini said the 28-nation EU had "no more excuses" now not to come up with a common response to the migrant tide.
"We need immediate action from the EU and the member states," she said.
EU president Donald Tusk said he would host an emergency summit on the crisis on Thursday.
Italian Prime Minister Matteo Renzi, whose country is among those bearing the brunt of the flood of migrants, said Rome was studying the possibility of mounting "targeted interventions" against the Libya-based people smugglers behind the crossings.
- An 'avoidable' disaster -
Europe's southern shores have been swamped over the past two weeks with migrants fleeing war and hardship, mostly via Libya.
In another tragedy, police in Greece reported three people killed, including a child, in the sinking of a boat off the island of Rhodes.
The sail boat ran aground on a crossing from Turkey.
Dramatic YouTube footage showed people trying to reach survivors huddled on a piece of wreckage as they were being swept by the waves towards the rocks. Ninety-three people were rescued alive, port police said.
Meanwhile, Italian and Maltese navy boats continued to scour the water for the victims of Sunday's disaster, which brings to an estimated 1,600 the number of migrants who have drowned in the Mediterranean this year, many times the toll over the same period last year.
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Only 28 survivors have been rescued so far, along with 24 bodies, which were taken to Malta.
One survivor told Italian authorities there were as many as 950 people on board and that some had been locked below deck by the smugglers.
The tragedy caused an outcry across Europe, where newspapers declared it the ""EU's darkest day".
Chancellor Angela Merkel of Germany, which is the top destination in Europe for migrants, said she was "appalled" by the disaster, calling it "not worthy of Europe".
Refugee and rights bodies demanded European governments beef up its sea rescue operations and address the underlying causes of the unprecedented migrant flows.
Malta's Prime Minister Joseph Muscat urged the EU to address the chaos in war-torn Libya, which people smugglers have made the main launching pad for rickety overloaded boats that often run out of fuel half-way.
Speaking at a press conference with Muscat Italy's Renzi said "the hypothesis of military intervention (to stabilise Libya) is not on the table... but what is possible are targeted interventions to destroy a criminal racket.".
Since the 2011 uprising that ousted longtime dictator Moammer Khadafi, Libya has been mired in chaos, with rival factions fighting it out for control of the oil-rich state.
Mogherini said that, just as the Islamist attacks in Paris in January had generated a common response, Sunday's shipwreck off Libya should give momentum to finding a common migration policy.
"The main issue here is to build a common sense of European responsibility, knowing that there is no easy solution," she added.
- Italy overwhelmed -
Some 11,000 migrants have been rescued since the middle of last week alone and current trends suggest last year's total of 170,000 landing in Italy is likely to be exceeded in 2015.
The issue of who handles these migrants -- for asylum or repatriation -- is hugely sensitive, with Italy complaining its EU partners are not doing enough.
Rome scaled back its Mare Nostrum search-and-rescue operation at the end of last year in protest over its rising cost.
It was replaced by a much smaller EU-led mission called Triton, which has been accused of doing too little to save lives.
Some EU states, especially those not directly affected by the arrivals, have been reluctant to commit more resources to the rescue effort but that could be changing.
The deadliest incident prior to Sunday occurred off Malta in September 2014, when an estimated 500 migrants drowned after traffickers deliberately rammed their boat in an attempt to force the passengers onto a smaller vessel.