Some 170,000 irregular migrants entered the European Union in September, the bloc's border agency Frontex said on Tuesday, taking the total for the year so far to 710,000.
That compares with 282,000 migrants crossing irregularly for the whole of 2014 as Europe faces its biggest refugee crisis since World War Two. Some of the increase may reflect double-counting, notably due to a surge in people arriving in Greece but then crossing the Balkans and re-entering the EU in Hungary.
In August, Frontex said in its latest statement, it recorded 190,000 irregular arrivals, many of them by sea to Greece, setting a fifth consecutive monthly record. It had earlier reported 156,000 irregular border crossings in August.
The rapidly collated figures on those people detected provide a rough monthly snapshot of migration flows. Statistics on asylum claims in the EU, which lag behind, showed some 400,000 people claimed protection at the bloc's borders in the first half of this year, compared with 625,000 in all of 2014.
In all, 350,000 people reached Greece from January to September, Frontex said, of whom 49,000 arrived in September alone, many of them Syrians.
A shortage of boats in Libya and worsening weather helped to halve the number of migrants arriving in Italy in September to 12,000, Frontex said, bringing the total for the first nine months in Italy to 129,000, many of them from Eritrea.
The total number of irregular border crossings include significant double counting. In the nine months to September, Hungary reported 204,000 people crossing its borders who did not have the appropriate passports and visas. That was a 13-fold increase on the same period in 2014. But, a Frontex spokeswoman said, some entering Hungary would already have been recorded as entering Greece before moving on across non-EU Balkan states.
September's EU aggregates also did not yet include an estimated 97,000 people who entered the EU in Croatia in the second half of last month after Hungary sealed its border with non-EU Serbia, Frontex said in its statement.
The European Union's struggles to deal with the flow of migrants fleeing poverty and turmoil in the Middle East and Africa has plunged the 28-nation bloc into crisis.
Leaders are due to discuss their responses again at a summit in Brussels on Thursday and Friday. Among items on the agenda are closer cooperation with Turkey, from where many Syria refugees reach Europe, and beefing up Frontex's ability to support national border guard services to control arrivals.
"Urgent assistance is needed, especially for Greece and Italy, to help register and identify the new arrivals," the border agency's executive director Fabrice Leggeri said, noting his request for hundreds of extra seconded staff for Frontex.
"I do hope we receive adequate contributions which will show the true spirit of European solidarity."
(Reporting by Alastair Macdonald; @macdonaldrtr; Editing by Philip Blenkinsop and Alison Williams)
