OSLO, July 24  -- The Norwegian anti-terror police on Thursday said they had been informed of a planned terrorist attack against the country.

At a hastily-convened press conference, Alana Bjoernland, chief of Norway's anti-terror police agency PST, announced that suspects associated with a terrorist organization in Syria plan to launch an attack in Norway in a few days.

The PST received the information from usually reliable sources, but is uncertain about where and when an attack would take place, the Norwegian news agency NTB said.

"There is a specific threat against Norway," said Norwegian Justice Minister Anders Anundsen, who also called on the Norwegian public to remain extra careful and attentive.

Norwegian Prime Minister Erna Solberg and the staff of the prime minister's office are focusing on dealing with the concrete threat and precautionary security measures have taken, said the justice minister.

Police throughout Norway are now on alert and armed police presence will be increased at places like border crossings, airports, train stations, said Vidar Refviksanden, acting chief for the Norwegian police force.