The sex attacker pounced on the 60-year-old woman as she left for work in Germany at around 6am last Friday.
The man, a foreigner in his 20s, followed the woman before attacking her in the street near her home in Jena, Thuringia.
He then grabbed the pensioner, dragged her into a driveway and subjected her to sexual abuse.
The woman managed to escape his clutches, but was almost hit by a car as she desperately fled into the road.
The man tried to tail the woman, but scarpered when he spotted a car coming.
The driver of the car reportedly swerved around the woman and did not stop to help.
Her attacker is described as a thin, 170cm tall Mediterranean man who spoke broken German.
He was wearing an orange hooded jacket with dark shades on the sides and was unshaven at the time of the alleged attack.
Police are now probing the incident and a manhunt is under way.
The incident is the latest sex attack to rock Germany after Angela Merkel took in more than a million refugees from the Middle East.
It comes after two migrants allegedly took turns to molest girls after trapping them in a swimming pool slide.
Police spokesman Tom Litges said: “The girls travelled down the chute but were stopped halfway down by the first attacker, and were unable to go any further when suddenly the second attacker then came up behind them and the two men put their hands on the girls' breasts and bottoms.
“They said that the two men had been taking it in turns to assault each of them.”
In a seperate incident, a refugee beheaded a woman in an ritual killing after stabbing her 30 times in Berlin.
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