Italian authorities found the lifeless bodies of two women aboard a migrant ship rescued in the Mediterranean, a discovery that further raised this week's high toll for refugee deaths across Europe and northern Africa.

The two died as they were trying to reach southern Europe on a boat carrying another 125 people, including five pregnant women and numerous children.

They were intercepted by the Italian coastguard off the Libyan coast and have now been disembarked in the Sicilian port of Messina along with other 588 asylum seekers rescued from other smugglers ships in recent days.

The bodies have been taken to a hospital for a forensic examination, with local media suggesting they died of asphyxiation.

Authorities said a second coastguard vessel has brought another 254 safely to land in Calabria while 415 more asylum seekers have arrived in the port of Taranto, Apulia, on a boat operated by charity Doctors Without Borders.

The fresh casualties came at the end of a dramatic week for migrant deaths that renewed urgency for EU leaders to agree a concerted response to the current crisis.

On Wednesday (26 August), 52 people died in the hold of a migrant boat headed towards Italy. A day later the decomposing bodies of 71 refugees were found inside a lorry in Austria, and finally on Friday 28 August two migrant vessels capsized off the Libyan city of Zuwara, killing up to 200 people.

Italian police have detained 10 suspected traffickers over the first tragedy, on suspicion of murder. Hungarian judges are due to decide whether to keep in custody four men authorities believe to be part of a smuggling ring responsible for the Austrian deaths.

The four, the three Bulgarians and an Afghan appeared before a court at a closed-doors hearing in the city of Kecskemet.

Austrian detectives said one of the men is the truck owner while two others are believed to have driven and then abandoned it on the hard shoulder of a highway near the eastern town of Parndorf, upon realising it carried a cargo of corpses.

UN Secretary General Ban Ki-Moon said he was "horrified and heartbroken" at the continuous loss of lives, and urged European government to act.

"These repeated tragedies underscore the ruthlessness of people smugglers and traffickers whose criminal activities extend from the Andaman Sea to the Mediterranean to the highways of Europe. It also highlights the desperation of people seeking protection or a new life," he said.

"I appeal to all governments involved to provide comprehensive responses, expand safe and legal channels of migration and act with humanity, compassion and in accordance with their international obligations," he added.

"This is a human tragedy that requires a determined collective political response. It is a crisis of solidarity, not a crisis of numbers."