A 37-year-old Romanian and a 54-year-old Greek citizen were arrested in Hamburg and in a Greek village respectively "on suspicion of attempted sabotage of a defence vessel", they said in a statement.

The men, who worked at the port at the time, are accused of putting more than 20 kilograms (about 40 pounds) of grit into a ship's engine block, puncturing water supply lines, removing caps from fuel tanks and deactivating electronic safety switches.

The attempted sabotage of the corvettes was discovered in time to avoid any further damage.

"Had the acts of sabotage gone undetected, they would have led to significant damage to the ships or, at the very least, delayed their departure, thereby potentially endangering the security of the Federal Republic of Germany and the armed forces' operational effectiveness," prosecutors said.

While Monday's arrest warrant relates to sabotage against one ship, the two men are also suspected of committing similar acts on other vessels.

Apartments belonging to the suspects in Hamburg, Romania and Greece were also searched in the operation coordinated through Eurojust, an EU agency based in The Hague.

German prosecutors said they were still investigating who could have been behind the alleged acts of sabotage.

Germany and other NATO members across Europe are on high alert over suspected Russian espionage, drone surveillance and sabotage.

Last week, parliament adopted a new law aiming to better protect German critical infrastructure from sabotage as well as from accidents and natural disasters.

Early last month, an arson attack claimed by a left-wing extremist group targeting electricity cables left tens of thousands without power in Berlin.