Egyptian prosecutors were interrogating on Tuesday an Israeli man, who is suspected of espionage, in the Red Sea port of Nuweiba, a judicial source said.
"An Israel man was arrested on Monday in Taba on suspicion of espionage. He was remanded today in police custody for four days pending investigation," the source said.
The suspect "infiltrated into Egypt through a mountainous area near Taba," the source added, without elaborating.
In October 2011, Egypt freed a US-Israeli citizen under a prisoner exchange after he was arrested in Cairo and accused of working for Israel's Mossad spy agency and sowing sectarian strife in Egypt, allegations he denied.
Israeli media identified the suspect arrested in Taba as 24-year-old Andrey Pshenichnikov, a Russian-born immigrant to Israel who had been arrested by the Israeli Shin Bet security service last year over his pro-Palestinian activism.
Haaretz newspaper said that he had served for 4 1/2 years in the Israeli military.
"After being released from the army, he underwent a dramatic political shift and started being active with radical left-wing organisations," it wrote on Tuesday.
"A year ago he moved to Bethlehem and after that to the Deheishe refugee camp," in the West Bank, it added.
"His time living among Palestinians ended when he was arrested by the Shin Bet and accused of being a member of a terror organization, but was later released after a court hearing."
Maariv daily said that he had tried to revoke his Israeli citizenship and in court said "that he did not recognise either the State of Israel or the Zionist establishment."
Israeli foreign ministry spokesman Yigal Palmor told AFP that there had so far been no formal notification from Egypt that any Israeli had been arrested there.
"We have asked the Egyptians for information," he said. "We are waiting to hear officially from the authorities what they suspect him of and what they intend to do. On that basis we shall know what we can do."