The number of migrants and refugees arriving in Italy and Greece since the start of the year has risen sharply compared to the same period 2015 and hundreds are stranded at European borders due to rising restrictions, aid agencies said yesterday.

At least 102,500 people have landed on Greek islands including Samos, Kos and Lesbos this year, and 7,500 in Italy, the International Organization for Migration (IOM) said in a statement.

"We've reached that figure in two months as opposed to last year when it was reached by the summer," IOM spokesman Itayi Viriri told a news briefing.

In 2015, the 100,000 mark was not reached until the end of June, according to IOM figures. The vast majority of the latest arrivals are from Syria, Afghanistan and Iraq, IOM said.

In a separate statement, the United Nations refugee agency called on European countries to take a "unified approach" and denounced restrictions limiting access for asylum seekers, including some based on nationality.

Referring to caps imposed by Austria and Slovenia, the UNHCR said: "These newest restrictive measures risk violating EU law and undermine efforts for a comprehensive and coordinated approach to deal with the refugee and migrant crisis in Europe."

"I am very worried about the news that we are getting about increasing closures of European borders along the Balkans route because that will create further chaos and confusion," UNHCR chief Filippo Grandi said during a visit to the Greek island of Lesbos.

Some 8,000 refugees and migrants have been trapped in Greece after Macedonia on Sunday barred passage to Afghans and introduced tougher document checks for Syrians and Iraqis.

Most of the refugees are fleeing war and persecution and deserve protection, including Syrian refugees from fierce fighting in Aleppo, the UN High Commissioner for Refugees (UNHCR) said in a statement.

"And yet, with every passing week, it appears some European countries are focusing on keeping refugees and migrants out more than on responsibly managing the flow and working on common solutions."

Last week Austria, Slovenia, Croatia, Serbia and the former Yugoslav Republic of Macedonia agreed to jointly profile and register refugees at the border between Macedonia and Greece, which had resulted in "increased protection risks", UNHCR said.

Austria and Slovenia's daily cap on asylum seekers and their joint restrictions with the other three countries had left nearly 700 people, mainly Afghans, barred from crossing from Macedonia into Serbia, UNHCR said.

Macedonia's own restrictions also left hundreds stranded at border crossings from Greece, where police started removing them on Tuesday, sources said.

More than 410 have died so far this year at sea, mostly on the route from Turkey to Greece, the IOM said.