Hackers carried out a major attack on Germany's centre-right Christian Democratic Union party, the Interior Ministry confirmed on Saturday.
The ministry did not provide further information about the extent or nature of the attack, which is being investigated by Germany's domestic security service, the Office for the Protection of the Constitution.
"However, the nature of the attack points to a very professional actor," a spokesman said.
The incident is being taken very seriously, according to sources close to the government.