BERLIN (Reuters) - The number of migrants coming to Germany needs to fall, German Vice Chancellor Sigmar Gabriel wrote in a letter on Tuesday, as data showed registrations almost tripled in January compared with the same month last year.

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The Federal Office for Migration and Refugees (BAMF) said Germany’s states registered almost 92,000 migrants last month in the computer system called EASY, which records people in reception centers and then distributes them around the country based on each state’s population and tax revenues.

The sharp rise was probably largely due to people who had arrived last year registering later since a backlog had built up, an expert at the interior ministry said.

The refugee crisis is a “test of endurance” said Gabriel, who is also economy minister, in his letter to members of his Social Democrat (SPD) party.

It comes as Chancellor Angela Merkel faces increasing criticism for her “open-door” policy, which saw more than 1.1 million migrants enter Germany last year. Gabriel’s SPD is the junior partner in Merkel’s ruling coalition.

Merkel has also said the number of refugees needs to go down and that most refugees from Syria and Iraq would go home once the conflicts there had ended.

The federal government in Berlin, as well as states and municipalities, was beginning to feel “how the political pressure is growing and how the right-wing populists are playing with people’s fears”, Gabriel said.

“That’s why Europe must succeed, in the first half of the year, in reducing the number of refugees who come to Germany every year,” he said.

Frauke Petry, leader of the right-wing Alternative for Germany (AfD) party, said at the weekend that migrants entering illegally should be shot if necessary.

Her remarks prompted Gabriel to say on Sunday that Germany’s domestic intelligence agency (BfV) should monitor the populist party, which should not be able to “excrete their slogans” on public television.