(Reuters) -A German army officer was sentenced to three years and six months in prison for spying for Russia, the Duesseldorf higher court said on Monday, in a case that highlighted Germany's vulnerability to the increasingly hostile neighbour to its east.

Judges found that Thomas H., then a captain stationed at the army's procurement office in Koblenz, had handed over internal documents to Russia's consulate in Bonn last May and had offered to provide more material in future.

"The documents he provided could provide a foreign power with information that would be adverse to Germany's security," judges said in their ruling.

The procurement office's activities are especially sensitive at a time when the European Union's economic powerhouse is racing to re-equip and rebuild its long-neglected armed forces in response to Russia's invasion of Ukraine.

The fact that Russia posed a military threat to Germany was an aggravating circumstance, judges ruled. Germany plays a central role in equipping Ukraine militarily for its defence against Russia.

Judges noted that the officer had no prior offences on his record, had not benefited materially from helping Russia and was in poor health at the time he did so. He regretted his actions and had cooperated with the investigation, they added.

(Reporting by Thomas Escritt, Editing by Rachel More and Andrey Sychev)