Extra police have been installed around Dresden's three mosques and Muslim prayer rooms following the two explosions by suspected xenophobic attackers, German media reported on Monday evening.

Security will also be boosted for the Day of German Unity celebrations, which are due to be held in the city on October 3 with German President Joachim Gauck and Chancellor Angela Merkel in attendance, officials said.

"We have now switched to crisis mode," said Dresden police chief Horst Kretzschmar, adding that no one had claimed responsibility for the blasts.

On Monday evening, two small bombs detonated in front of a mosque and a convention center, which was due to play host to the 26th anniversary reunification commemorations.

Blasts in quick succession

The first blast occurred at 9:53 pm local time (1953 UTC), outside a mosque in the eastern neighborhood of Cotta. An imam was inside the building at the time, along with his wife and two children.

About half an hour later, a second explosion was heard outside the International Congress Center, forcing police to evacuate the nearby Maritim Hotel.

According to German media, both buildings were damaged but no one was injured.

The blasts also coincided with a ceremony in Berlin to mark the tenth anniversary of the German Islam Conference, a forum to improve dialogue between the government and Muslim communities.

Dresden has come under criticism for far-right politics and xenophobia in recent years, beginning with the anti-Islamization PEGIDA movement founded in the city in October 2014. Monday's bombings came just after PEGIDA staged its latest march through the city.

The state of Saxony has also been the scene of several violent clashes outside refugee shelters.

mm/kms (AFP, dpa)