German media reports say two teenagers have been arrested on suspicion of planning and preparing an attack on a Christmas market.

North Rhine-Westphalia's state interior minister said on Wednesday that a 15-year-old boy in the state was arrested.

Local media say the boy had announced an attack on Friday December 1 in a video posted on social media.

Reports say he was in online contact with another teenager in a different state, who has also been arrested.
The two teenagers reportedly discussed plans to attack a Christmas market in Cologne or a synagogue, using a truck or other devices.

Also on Wednesday, the head of Germany's intelligence agency warned of a heightened risk of terror attacks in the country.

In a statement, he said international terrorist groups such as Al-Qaeda are increasing their activities amid the Israel-Hamas conflict.

He said there are risks that people with extremist ideas could be inspired to carry out attacks targeting outdoor events.

Fears of terrorism and attacks on Jewish people are rising in Europe in the wake of the conflict in the Middle East.

German authorities are likely to step up security at Christmas markets and other seasonal events.