Austria said on Friday 71 refugees including a baby girl were found dead in an abandoned freezer truck, while Libya recovered the bodies of 82 migrants washed ashore after their overcrowded boat sank on its way to Europe and scores more were feared dead.
The U.N. refugee agency said the number of refugees and migrants crossing the Mediterranean to reach Europe had passed 300,000 this year, up from 219,000 in the whole of 2014.
Three Bulgarians and an Afghan were arrested in connection with the truck deaths. The victims - 59 men, 8 women and four children, including a girl of 1-2 years old - were probably from Syria, police said.
At least 180 were either dead or missing in the Libyan disaster. Both tragedies were a result of a renewed surge in migrants seeking refuge from war and poverty that has confronted Europe with its worst refugee crisis since World War Two.
The U.N. refugee agency (UNHCR) said more than 2,500 people have died making the sea crossing this year, compared with 3,500 who died or went missing in the Mediterranean in 2014.
German Chancellor Angela Merkel said European Union leaders were ready for an emergency meeting, if needed, to discuss the refugee crisis.
A security official in the western Libyan town of Zuwara, from where the doomed migrant boat had set off, said there had been around 400 people on board. Many appeared to have been trapped in the hold when it capsized on Thursday.
"About 100 people are still missing," said Ibrahim al-Attoushi, a Red Crescent official, and 198 had been rescued.
The migrants were from sub-Saharan Africa, Pakistan, Syria, Morocco and Bangladesh, the security official said.
The Libyan coast guard has limited capabilities, relying on small inflatables, tug boats and fishing vessels.
Zuwara, near the Tunisian border, is a major launchpad for smugglers shipping migrants to Italy.
Libya is a major transit route for migrants hoping to make it to Europe. Smuggling networks exploit the country's lawlessness and chaos to bring Syrians into Libya via Egypt while Africans arrive through Niger, Sudan and Chad.
The Italian coast guard said 1,430 people had been rescued in operations off Libya on Thursday, and a merchant ship sent to the aid of a small boat carrying 125 people recovered two bodies.
In Greece, coast guards said they had rescued more than 1,600 migrants making their way to Greek islands near Turkey over the past three days.
Police in Sicily detained 10 people on suspicion of multiple homicide and aiding illegal immigration after 52 migrants were found dead in the hull of a boat this week.
In Europe, refugees and migrants have swept north through the Balkans in recent days, with thousands of Syrians, Afghans and Pakistanis crossing from Serbia into EU-member Hungary, where authorities said more than 140,000 had been caught entering the country so far this year.
Almost all hope to reach the more affluent countries of northern and western Europe such as Germany and Sweden.
Hungary, which is part of Europe’s Schengen passport-free travel zone, is building a high fence along its border with Serbia to confront what it says is a threat to European security, prosperity and identity.
Hungary plans to tighten laws next week to curb migration pressure on the country, including using the army, if needed, to help police near the southern border, lawmaker Gergely Gulyas of the ruling Fidesz party said on Friday.
Austrian police had originally put the death toll in the truck found abandoned near the Hungarian border on Thursday at about 50, but later raised the figure to 71.
The refrigerated vehicle was found by an Austrian motorway patrol with fluids from the decomposing bodies seeping from its back door.
The truck is at a customs building in the village of Nickelsdorf, which has refrigeration facilities and where forensic specialists in white protective suits and yellow rubber boots could be seen wheeling body bags away.
In Hungary, police said 10 Syrian migrants were injured on Friday when a van driven by a Romanian suspected of human trafficking overturned en route for Budapest.
The UNHCR said that in one incident on Thursday, 51 people suffocated in the hold of a boat and survivors said they had been beaten to force them into the hold and then had to pay money to smugglers just to come out to breathe.
One of the survivors, an Iraqi orthopedic surgeon, said he had paid 3,000 euros ($3,400) to come up on to the top deck with his wife and two-year-old son.
Last week, 49 people died in another boat's hold after inhaling poisonous fumes, and on Wednesday 21 people are thought to have died after a dinghy with 145 on board got into difficulty, UNHCR spokeswoman Melissa Fleming said.