Merkel booed during refugee home visit

Far-right demonstrators have booed German Chancellor Angela Merkel during a visit to a refugee centre hit by violent protests, in a display of anti-migrant sentiment over the record influx of asylum-seekers.

About 200 people in the eastern town of Heidenau shouted "traitor, traitor" and "we are the mob" - a reference to a leading German politician's use of words to condemn the protesters.

Merkel vowed that Germany would have "no tolerance" for "shameful and vile" attacks on asylum-seekers, after a wave of violent protests.

"There will be no tolerance of those who question the dignity of other people," she said in the small eastern town of Heidenau.

"The more people who make that clear ... through their work and also in conversations with acquaintances, friends and families, the stronger we will be and the better we will be able to address this task" of caring for refugees.

Earlier President Joachim Gauck blasted a "dark Germany" behind a series of xenophobic attacks on refugee shelters after two fresh assaults were reported in the east of the country on Wednesday.

Visiting a shelter in Berlin, Gauck said the expected arrival of up to 800,000 asylum-seekers this year - four times last year's total - was bringing out the best and worst in Germans.

The president praised the many "volunteers who want to show that there is a Germany in the light, a shining contrast to the dark Germany we witness when we hear about attacks on refugee centres or even xenophobic acts against people".

A man was seen hurling a Molotov cocktail into a refugee home in the eastern city of Leipzig which was due to house 56 asylum-seekers from Wednesday, police said.

Only a mattress was burned as a witness was able to raise the alarm swiftly.

Meanwhile in the town of Parchim, also in eastern Germany, police arrested two men who had charged into a refugee shelter wielding a knife.

Several residents, who were outside when the incident took place, alerted the police after noticing that one of the two suspects was holding a 20.5cm knife.

Both were shouting anti-migrant slogans. Police ran blood tests on them for alcohol levels.

German authorities have been alarmed by a wave of attacks targeting refugee centres, with more than 200 incidents reported this year.

Gauck said most Germans had proved "open to and ready to help" the newcomers fleeing war and poverty and that their welcome should not be destroyed by "rabble-rousers and arsonists".

The German government had earmarked an additional 500 million euros ($A803.98 million) for towns and cities to house, feed and care for refugees, bringing the total to one billion euros.