Some 50 migrants were found dead in the hold of a boat off the coast of Libya yesterday during a rescue operation which saved 430 other people, the Italian coast guard said.
Thousands of people, mainly from Africa and the Middle East, have put to sea this year in the hope of reaching Europe, often dangerously packed on to small boats that were never designed to cross the Mediterranean.
A spokeswoman for the Italian coast guard said the Swedish ship Poseidon, working with the EU's border control agency Frontex, had gone to help a boat in difficulty and had found the bodies. It was not immediately clear how the migrants died.
More than 100,000 migrants have reached Italy so far this year, but at least 2,300 are believed to have died while trying to make the crossing.
Emergency services received 10 calls for help from various boats in difficulty yesterday, all in an area around 50km from the Libya coast, the spokeswoman said.
An Italian coast guard vessel saved 113 people from a partially-deflated rubber boat, but one passenger, who was already fighting for their life, died soon after.
Meanwhile, traumatised migrants surged across the Serbian border into Hungary.
Then they jostled to formally enter the country so they could quickly leave it, heading toward more prosperous EU nations on a desperate quest to escape war and poverty.
In Roszke, a Hungarian border town, migrants mostly from Syria, Iraq and Afghanistan requesting asylum were being processed by authorities.
Police used tear gas to break up a brief scuffle involving about 200 migrants, saying the migrants were growing impatient with delays in the registration process caused by the growing number of arrivals.
So far, most of the Hungarian border fence - which is being hastily built to keep the migrants out - consists of three layers of razor wire, which the government says will be completed this month along its 174km border with Serbia.
But the fence did not stop one group of migrants, including women and children, from crawling under it yesterday. Using blankets, sleeping bags, jackets and a stick, they raised the wire. As a police car approached, they dashed through a nearby field.
"Very, very difficult," said Odei, a Syrian migrant from Daraa. "We raised the fence and crossed it now. We were here from yesterday. We are very hungry. There's no food, there's no medicine for children, there's nothing. We are so tired."
The migrants are following the Balkans route, from Turkey to Greece by sea, up north to Macedonia by bus or foot, by train through Serbia and then walking the last few miles into EU-member Hungary.
The route avoids the dangerous Mediterranean Sea crossings of those trying to reach Italy from North Africa.
Over 10,000 migrants, including many women with babies and small children, have crossed into Serbia over the past few days and then headed toward Hungary.
The flood follows Macedonia's decision to lift a three-day blockade of its border with Greece after thousands of migrants simply stormed past Macedonian police.
By early yesterday morning, 1,302 migrants had already been detained at Hungary's southern border with Serbia, according to Karoly Papp, Hungary's national police chief.
Police said 2,533 migrants were detained on Tuesday, up from 2,093 on Monday, with the numbers setting records nearly every day.
Hungary is still scrambling to react. Mr Papp said over 2,100 police "border hunters" would be deployed beginning on September 15, with helicopters, police dogs and patrols on horseback taking part in the effort to secure the border. Water cannons will also be sent to Szeged, the largest city in the region.
"The organisation, equipment and great mobility of the border guard units ... will decrease the security risks caused by the massive illegal migration," Mr Papp said.
The hard-hit border nations of Greece, Italy and Hungary have urged the EU and fellow European nations to do more to help share the heavy migrant burden this year, but some nations are refusing to do so because of strong public anti-migrant sentiment or budget constraints.