Austrian police have warned of a possible "Islamist-motivated attack" in Vienna against churches, citing undisclosed information the country's intelligence service had received.

Police in Vienna tweeted that they had heightened security in front of certain buildings, including churches, and increased the presence of officers in the Austrian capital.

"There is a non-specific threat of an assault against churches," Vienna police tweeted on Wednesday.

"As precautionary measure ... points of interest have been put under increased guard by regular and special operation police forces."

Police said they could not say how long their security measures would remain.

"Police officers are equipped with bulletproof helmets and vests and assault rifles. They will carry out surveillance activities and also carry out checks in road traffic," police spokesman Markus Dittrich told local radio station Radio Wien.

He did not give any further details on the background of the threat but said that more police would be seen patrolling near churches.

Vienna is among the safest capitals in the world and militant attacks are rare. The first deadly attack in a generation took place in 2020 when a jihadist gunman killed four people in a shooting rampage before being shot dead by police.

AP with Reuters