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", prosecutors said in a statement.

The men, who worked at the port at the time, are accused of putting more than 20 kilogrammes (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.

According to newspaper Der Spiegel, a total of seven cases of attempted sabotage are being investigated involving five different vessels built at the premises of the Blohm+Voss shipbuilding company.

One of incidents in early 2025 targeted the corvette Emden, while another in June of the same year took place on the corvette Koeln, the paper reported.

They are both part of a group of five vessels built for the German navy since 2019 in an effort to modernise and strengthen the fleet.

- Search for mastermind -

Der Spiegel reported that the two suspects worked for a company offering services such as corrosion protection for ships and that investigators became suspicious when they noticed the times of the attacks overlapped with the men's working hours.

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

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

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

Last week, Germany's parliament adopted a new law aiming to better protect the country's 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.