More than 1,500 mostly Syrian refugees, trapped in no-man's land for three days, have entered Macedonia from Greece without any attempt by the police to stop them.

Key points: More than 1,500 refugees entered Macedonia after being trapped between Greek-Macedonian border

More than 1,500 refugees entered Macedonia after being trapped between Greek-Macedonian border Police said no more would be allowed to enter until current group moves north

Police said no more would be allowed to enter until current group moves north Italy's coastguard rescued about 2,200 migrants in the Mediterranean

Macedonian police had earlier used stun grenades and batons in a bid to stop hundreds of refugees breaking through barbed wire fencing on its southern border with Greece, but on Saturday evening they allowed all the migrants into the country.

Police officers were seen guarding the frontier but not a single person remained in the strip of land between the Greek-Macedonian border where more than 2,000 people, including women and children, had been stuck since Thursday.

The migrants hope to cross into Serbia in the north and eventually start a new life in the European Union.

Macedonian police spokesman Ivo Kotevski said police did not want to use force to stop the migrants and refugees, but would continue to control the flow of new arrivals.

"We will continue with reinforced control of the border according to the state of emergency and we will [in future] allow only a limited number of people into the country in accordance with the capacities we have," Kotevski said.

He said no new people would be allowed to enter until the current group had moved on towards the north "or we will have a humanitarian crisis in Macedonia".

Thousands of refugees and migrants, mostly from Syria, Iraq and Afghanistan, are expected to arrive in the country in the coming days after being ferried to the Greek mainland from the islands.

Authorities deny being heavy-handed

On Thursday, Macedonia declared a state of emergency and sealed its border in a bid to stop the influx, after news several hundred would be let through every few hours reached those on the border and a crush formed after the first group streamed through.

Macedonians officers twice resorted to force to try to prevent people from entering the country and at least a dozen were hurt in the brief flare-up.

Amnesty International said it spoke to some refugees who gave accounts of police beatings and shots being fired in the air but authorities denied being heavy-handed.

Events on Thursday and Friday saw Macedonia become the latest flashpoint of a crisis that has dragged the conflicts of the Middle East — most notably Syria — to Europe's doorstep.

Macedonia said it had registered more than 40,000 migrants and refugees entering from Greece in the past two months.

Most move quickly through the country to Serbia and then walk into Hungary and on to the more affluent countries of western and northern Europe through the borderless Schengen Area.

No new refugees will be allowed to enter Macedonia until the current group has moved north. ( Reuters: Ognen Teofilovski )

Another 2,200 migrants rescued off Italy

The Italian coastguard has coordinated the rescue of 2,200 migrants in the Mediterranean after receiving distress calls from more than 20 overcrowded vessels drifting in waters off Libya in one of the biggest single-day rescue operations to date.

The operation was ongoing as nightfall approached on Saturday, and it was unclear how many people remained in danger.

Initial estimates put the total number of people on board the stricken ships at up to 3,000.

Two navy ships, the Cigala Fulgosi and the Vega, picked up 507 and 432 migrants respectively from two wooden boats in danger of sinking just off Libya, the navy said.

The coastguard said its patrol boats had safely boarded just under 300 people from three different inflatable dinghies.

Another 1,003 rescued migrants and refugees were reported to be headed for Italian ports on other boats, as the wave of new arrivals triggered increasingly virulent attacks on Prime Minister Matteo Renzi's handling of the migration crisis.

"This must a joke. We are using our own forces to do the people smugglers' business for them and ensure we are invaded," said Maurizio Gasparri, a senator for Silvio Berlusconi's centre-right Forza Italia party.

Leader of the anti-immigration Northern League party Matteo Salvini called on the government to park the migrants on disused Italian oil rigs off Libya.

"Help them, rescue them and take care of them: but don't let them land here," he wrote on his Facebook page.

The rescued migrants included a batch of 311, including a newborn baby, who were on a boat belonging to humanitarian group Doctors Without Borders, which is expected to dock in Vibo Valentia in Calabria, port authorities said.

A further 370 had been picked up by the Italian customs police and were headed for Messina in Sicily while some 322, Italian media said, were on the Norwegian boat Siem Pilot, part of the European Union's Triton mission.

More than 104,000 migrants and refugees have landed in Italy this year after being rescued in the Mediterranean. ( Reuters: Antonio Parrinello )

Passengers locked below deck on overcrowded vessel

More than 170,000 migrants and refugees from Africa, the Middle East and South Asia landed at Italy's southern ports in 2014 after being rescued in the Mediterranean, while the total for 2015 has already topped 104,000.

A further 135,000-plus have landed in Greece since January and more than 2,300 people have died at sea while trying to make it to Europe with the help of traffickers.

Police in Palermo, Sicily, announced on Saturday that they had arrested six Egyptian nationals on suspicion of people smuggling following the rescue of a stricken boat on August 19.

Testimony from the 432 migrants on board suggested the vessel had been packed with more than ten times the number of people it was designed for, with many of the passengers, including a number of women and children, locked below decks.

They had each paid the traffickers 2,000 euros ($AU3,100) for the passage from Egypt to Italy, according to statements given to police.

On board, the crew were reported to have demanded further payment to allow those locked in the hold to come up temporarily for air.

Humanitarian organisations said the surge in the numbers of people trying to reach European Union countries was the result of conflicts and repression in Africa and the Middle East.

They have called on European governments to shoulder more of the burden of absorbing the wave of asylum seekers and to help create safer routes for them to reach Europe.

AFP