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BERLIN (Reuters) - Fear of terrorism, political extremism and social tension due to mass migration are Germans’ top concerns as they prepare to vote in a federal election, a survey showed on Thursday.

Worries about jobs and the economy have meanwhile fallen to record lows, according to the annual study by insurer R+V.

Having presided over an economic upswing that has boosted wages and created jobs, Chancellor Angela Merkel is widely expected to win a fourth term in the Sept. 24 election.

Some voters from her conservative alliance have however defected to the anti-immigrant Alternative for Germany (AfD) over her decision in 2015 to open Germany’s borders to hundreds of thousands of refugees fleeing war in Syria and Iraq.

The R+V study showed terrorism remained the top fear, worrying 71 percent of Germans compared to 73 percent last year,

Security officials have said the country should brace for further violence by Islamist militants after it was hit by five attacks in 2016, including one in December on a Berlin Christmas market that killed 12 people.

“The fear of terror attacks is clearly in first place and is at one of the highest levels that has ever been measured,” said Brigitte Roemstedt, who heads the R+V Info Centre that surveyed around 2,400 Germans.

Political extremism was the second biggest worry, troubling 62 percent of Germans compared with 68 percent last year, while 61 percent fear that immigration could provoke social tension, down from 67 percent.

R+V said fear of unemployment and a poor economic situation were at record lows, while concerns about natural disasters and contaminated food had increased.