Chancellor Angela Merkel has urged Germans to stand up against hatred and vowed zero tolerance for attacks against refugees, as more than 100 far-right protesters booed her during a visit to a shelter for asylum-seekers.

Merkel had travelled on Wednesday to Heidenau, a small town near Germany's eastern border with the Czech Republic, to express support for refugees following neo-Nazi riots over the weekend at a hardware store that had been converted into a shelter.

On Tuesday, a school sports hall converted into an emergency refugee shelter caught fire in the eastern town of Nauen, in what police suspect was an arson attack.

In Heidenau on Friday and Saturday, dozens of police were injured when a far-right mob hurled bottles and fireworks at officers in an attempt to prevent the asylum seekers moving into the former hardware store.

"It's shameful and repulsive what we experienced here," Merkel said, after arriving in Heidenau, which is located south of Dresden.

A couple of hundred metres away, far-right protesters jeered and sounded car horns. Some protesters held placards denouncing the government, while others shouted "traitors" and "lying press."

Speaking to reporters after meeting aid workers, local officials and some of the 560 refugees at the site, Merkel praised those "who have to endure hatred".

"We need to use all our strength to make clear that we won't tolerate those who call the dignity of others into question," Merkel said.

"There will be no tolerance toward those who aren't prepared to help where help is needed," she said, urging Germans to speak out against anti-foreigner sentiment in conversations with their families, friends and church groups.

President visits asylum centre

Elsewhere, President Joachim Gauck visited a reception centre for asylum-seekers in Berlin-Wilmersdorf, where he thanked students, doctors and others who had volunteered to help refugees there and elsewhere across the country.

"They want to help, they want to show that there's a bright Germany full of light, as opposed to the impression we get of a dark Germany when we hear about attacks on asylum seekers," Gauck said.

German officials say the country faces a huge challenge finding adequate housing for the tens of thousands of asylum seekers arriving in the country each month.

Authorities predict the number of refugees coming to Germany will rise to 800,000 by the end of 2015 - a four-fold increase on last year.

While most Germans have been welcoming to the refugees, a minority has vocally opposed them.

Attacks against refugees and asylum centres roughly doubled to 202 during the first half of the year, including eight cases of arson.

Police arrested two intruders with knives entering a refugee home in Parchim in east Germany late on Tuesday.

The same night, a man threw a burning object at a planned home for 56 refugees in Leipzig.

A mattress caught fire, but it was quickly extinguished, the German news agency DPA reported.

Source: Reuters