More than 540,000 migrants escaping terror and poverty arrived on the Greek islands in the first 10 months of the year, 13 times more than in the same period of 2014, according to the European Union border control agency Frontex.

The Warsaw-based agency said Tuesday that more than 150,000 people made the journey from Turkey to Greece in October alone despite worsening weather conditions. That compares to 8,500 in October 2014.

Meanwhile, the numbers of people trying to reach Europe from Libya has been falling due to a shortage of boats available to smugglers.

That number was 8,500 in October, half of the number that made the trip in October of the previous year. The total for the year so far is 140,000 compared to 155,000 for all of 2014.

Greek authorities say more than 10,000 refugees and economic migrants have crossed from Greece into Macedonia since Monday morning, on their long trek toward wealthier western and northern European countries.

Macedonian border police were letting groups of 50 across at regular intervals Tuesday. But large bottlenecks formed due to increased flows toward the border crossing at Idomeni after migrants were stranded on the Greek islands for days by a ferry strike.

On Monday, about 2,000 people who were fed up with waiting up to 11 hours for their turn forced their way into Macedonia, but no injuries were reported.

Nearly all the migrants at Idomeni reached the Greek islands in frail boats from Turkey, paying large sums to smuggling gangs. On Monday, port authorities on the eastern island of Lesbos, where most migrants arrive, rescued 345 people who had been crammed into a luxury cruiser that ran aground just offshore.

Meantime, Slovenia's prime minister says that "in the next few days" the country will start building razor-wire fences on the border with Croatia to stem the flow of migrants, but not to stop it entirely.

Prime Minister Miro Cerar said that "at this moment about 30,000 immigrants are on their way toward Slovenia."

Slovenian officials have said a fence could be used to direct the refugee flow, not close the 400-mile border as was the case in Hungary.

Cerar has said previously that his small Alpine nation was being overwhelmed by the flow of refugees.

Nearly 170,000 migrants crossed Slovenia since mid-October when Hungary closed its border with Croatia and the flow was redirected to Slovenia.

The Associated Press contributed to this report.