Arrests in Germany over 'Cologne cathedral attack plot'

German police arrested three people on Sunday over an alleged attack plot targeting the cathedral in Cologne on New Year's Eve, AFP reported. 

The "alleged means of attack" is a car, said police in the western city, adding that security measures have been stepped up around the site.

The three suspects are believed to be linked to a Tajik who was arrested on Christmas Eve, said Cologne police chief Johannes Hermann.

The Tajik was detained by German police on the same day as Austria announced the arrests of another three suspects in Vienna.

Bild daily had reported then that the four are all Tajiks who allegedly wanted to carry out attacks for Islamic State-Khorasan (IS-K), an IS offshoot in Afghanistan.

Investigations following the Tajik's arrest a week back had found that there is a plot to deploy a car as a means of attack, but "in which way is not known to us," said Frank Wissbaum of Cologne police.

Officers had deployed sniffer dogs to search the underground parking of the cathedral for explosives but they have not yet turned up anything suspicious.

Nevertheless, protective measures have been significantly stepped up, with around 1,000 police officers deployed since this afternoon to "protect the cathedral and the population in Cologne city centre".