Traditional Christmas markets are opening across Germany amid heightened security, almost a year after a terror attack on a Berlin Christmas market killed 12.

German Interior Minister Thomas de Maiziere called on Germans Monday not to stay away out of fear, saying "Christmas markets are part of our life and culture."

But he also said that, "the terror threat is simply very high. Anytime. Anywhere."

The Berlin Christmas market, where a Tunisian attacker rammed a truck into visitors on Dec. 19, is to open Monday night with a candlelight ceremony.

Like most Christmas markets in Germany, it has been fortified with concrete blocks to stop possible car attacks and will have an increased presence of police officers. On the anniversary of the attack, the Berlin market will remain closed.