A NATO airbase in western Germany said Thursday it had raised its security level over a "potential threat".

"We raised the security level at NATO Airbase Geilenkirchen based on intelligence information indicating potential threat," the base said in a post on social media platform X.

The announcement comes just over a week after a German military base was sealed off for several hours as authorities investigated suspected sabotage.

The base in Cologne-Wahn was locked down after a hole was discovered in a fence near drinking water storage facilities.

But test results eventually showed that the tap water was not contaminated, according to the German army.

At the same time, NATO announced an attempted trespassing incident at the Geilenkirchen base.

An individual attempted to enter the base but was stopped and sent away, a spokesman said.

No link between the two incidents has been established.

Germany -- a key ally of Kyiv -- has been on high alert for sabotage and attacks on military facilities in the country in the wake of Moscow's 2022 invasion of Ukraine.

In April, investigators arrested two German-Russian men on suspicion of spying for Russia and planning attacks in Germany -- including on US army facilities -- to undermine military support for Ukraine.