Police have launched an online portal seeking tips about an arson attack on a synagogue in the northern German city of Oldenburg last Friday that prompted widespread outrage.

An incendiary device was thrown at the front door of the synagogue. Two janitors at a neighbouring cultural centre discovered the fire and extinguished it. No one was injured, but the perpetrators managed to escape and have not been identified.

Police investigating the crime announced the portal for tips on Thursday, and added that videos and photos could also be uploaded to the site.

A reward of €5,000 (about $5,400) has also been offered for tips that help solve the crime and identify the perpetrators.

The incident made headlines nationwide in Germany and prompted expressions of outrage and horror from leaders.

On Sunday, about 400 people took part in a rally in Oldenburg organized by a local alliance against anti-Semitism.