Romania has arrested two employees of an Israeli intelligence company on charges of spying on and trying to intimidate the country's chief anti-corruption prosecutor, officials say.

"An investigation has been launched and two people have been arrested," Mihaela Porime, a spokeswoman for the anti-crime and terrorist prosecutors' office, said on Wednesday, adding that the suspects work for the Israeli private intelligence agency, Black Cube.

The firm reportedly has several former operatives of Israel's Mossad spy agency on its payroll.

The pair were identified as Belgian David Geclowitz and Israeli-born Ron Weiner, who holds a French passport.

They are suspected of hacking the emails of people close to Laura Codruta Kovesi, the chief prosecutor of Romania's National Anti-corruption Directorate (DNA), and of threatening and harassing her family members.

The arrest warrant said the two had in March set up a "criminal group ... aimed at sullying Kovesi's image."

According to Romanian judicial sources, the two are believed to have been employed by a client being investigated by the DNA.

Meanwhile, Kovesi confirmed that the detentions were “linked to a failed intimidation bid.”

Kovesi, who was appointed last month for a second term as Romania's chief anti-corruption prosecutor, is known for her tough approach to high-level graft.

Her agency prosecuted some 1,250 cases only in 2015, with targets including a former premier and five ex-ministers.