The head of the Federal Office for Migration and Refugees (BAMF) said Monday it still had to work through some 430,000 applications that are pending.

BAMF President Frank-Jürgen Weise told reporters in Nuremberg the agency was also preparing to process around half a million new claims from migrants arriving this year. Meanwhile, bids are also expected from as many as 300,000 other migrants who have registered in Germany but haven't yet submitted their claims.

Weise warned that longer processing times could turn more people against refugees and against BAMF's work.

"The long wait for people who have fled is very difficult," he said. "If we drag these applications into next year, my concern is there'll be more criticism directed at the refugee issues and the work of our agency."

Germany took in some 1.1 million migrants in 2015 - the largest influx since World War II. However, it can often take months before new arrivals can formally apply for asylum.

Many refugees hoping to reach western Europe are camping out at Idomeni at the Greek-Macedonian border

Expanding efforts

In a bid to deal with the backlog of old applications, as well as new claims, BAMF has plans to speed-up its processing of asylum seekers at new arrival centers around the country. By mid-year they hope to have centers set up in each state.

More than 60,000 applications were lodged with BAMF in April - up nearly 125 percent over the same month last year, but only 1.6 percent higher than March. The largest number of claims (25,791) came from Syrians, followed by Iraqis, Afghans and Iranians.

Currently, some asylum applications - for example from Syrian refugees - can be processed within a week. But people from more "complex countries," where the reason for flight may not be as clear, have to wait an average of three to six months to hear back about their claims.

BAMF also aims to expand its workforce to handle the extra work. In early 2015, the authority had around 2,300 staff. It currently has 6,700 employees, with plans to expand that to 7,300 staff.

Drop in new arrivals

Despite high numbers of asylum applications, the number of people actually arriving in Germany has dropped significantly since the start of the year.

According to figures provided by the Interior Ministry on Monday, April saw some 16,000 new arrivals, down from around 21,000 in March, 61,000 in February and 92,000 in January.

One of the main reasons for the decline is the closure of the Balkan migrant route in early March, which left thousands of refugees stranded in Greece.

nm/kms (AP, KNA, epd, dpa)