BERLIN, March 11 (Reuters) - Police in the western German city of Essen have ordered a shopping centre in the centre of town to remain closed on Saturday due to "concrete indications about a possible attack".

"The current state of our investigations points to the threat being exclusively at the shopping centre," said the police in a statement, adding it could give no further details about the nature of the threat.

Germany is on high alert following major radical Islamist attacks in France and Belgium and after a failed asylum seeker from Tunisia drove a truck into a Christmas market in December, killing 12 people. (Writing by Madeline Chambers; Editing by Toby Chopra)