Berlin authorities on Christmas Day said their probe was focused on attempted arson stemming from a presumed suicide bid, saying their practice in such situations was to withhold details.

The 58-year-old driver sustained minor injuries and was being treated in hospital for a head wound, police added.

Late on Sunday, just before midnight, the blue-colored car crashed through the first set of glass doors of Willy Brandt House, the headquarters of the center-left Social Democratic Party (SPD).

Police later on Monday said the man had also admitted placing a bag containing gas cartridges and barbecue lighting substances outside Konrad Adenauer House, the headquarters of Chancellor Angela Merkel's conservative Christian Democrats (CDU).

A CDU center doorman had noticed an unknown person depositing the bag about an hour before midnight on Sunday.

Scorch marks

At the SPD headquarters, initial flames were quenched by the building's sprinkler system. Pictures from the scene showed burn marks and melted seat coverings and fittings.

Fire-deformed fuel canisters at the entrance

Controversial exploratory talks

The SPD is part of Chancellor Angela Merkel's post-September election caretaker cabinet and is about to open exploratory talks on whether to govern as partner for another four years, a prospect rejected by some who would prefer opposition.

Investigations on Monday were in the hands of Berlin police and the city-state's security services.

The German capital is still on edge after its December 2016 attack when a terrorist hijacked a truck and killed 12 people at a central city Christmas market.

ipj/rc (Reuters, dpa)