BERLIN - The number of attacks and other criminal offenses committed against refugee shelters in Germany has more than doubled this year compared to 2014, police said on Monday.Germany expects a record-breaking number of 800,000 new arrivals this year. The unprecedented influx of foreigners has fueled social tensions and there have been protests and attacks against asylum shelters in some parts of the country."In the last few months, the crimes have reached a new level - both in quantity and quality," Sandra Clemens, spokeswoman for the BKA Federal Criminal Police Office, told Reuters.The number of criminal offenses against asylum shelters so far this year surged to 437 from around 200 in the whole of 2014, she said, adding that damage to property, graffiti and verbal insults made up the largest part of the offenses.The total for 2015 included 59 crimes classified as violent, a new record high after last year's peak of 28, Clemens said. Of this year's figure, 26 were arson attacks.Police have arrested 20 suspects in connection with these arson attacks, she said. As a whole, police identified 500 suspects for crimes against asylum shelters.The majority of these suspects were men aged between 18 and 25 years who often lived in the same town where the offenses were committed, Clemens noted.The police statistics came after President Joachim Gauck warned that there are limits to how many refugees Germany can take in, showing growing concern even at the highest level over how to look after so many newcomers.