BERLIN (Reuters) -German prosecutors have arrested three foreigners - a Ukrainian, a Russian and an Armenian - on suspicion of working for an unnamed foreign secret service, the Federal Prosecutor's Office said on Friday.

Officials identified the three only as Ukrainian national Robert A., Armenian national Vardges I. and Russian national Arman S.. It said they had traveled to Germany on behalf of a foreign secret service to collect information on a Ukrainian who was staying there.

On June 19, they scouted out a cafe in Frankfurt where the target person was supposed to be, the prosecutors' statement said.

The arrests were another case in a slew of espionage cases that hit Germany in recent months.

Those include an alleged Russian sabotage plan at U.S. military facilities, an EU lawmaker's staffer suspected of spying for China, as well as three Germans who were supposedly handing over sensitive technology to China.

A report this week by Germany's domestic security service said Russia has turned increasingly to blackmail and financial incentives to hire Germans to spy for it after the blow dealt to its intelligence services by Europe's expulsion of some 600 Russian diplomats. Russia has previously denied German allegations of espionage.

(Reporting by Andrey SychevEditing by Matthias Williams and Frances Kerry)

By Andrey Sychev