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Police released surveillance photos of a man suspected in a kidnapping and sex assault at 2:10 p.m. March 25 in the 1800 block of San Pablo Avenue.

OAKLAND -- Police are looking for a man who grabbed and sexually assaulted a woman walking near downtown Oakland on Tuesday afternoon.

The 27-year-old woman was at 18th Street and San Pablo Avenue at 2:10 p.m. when a man grabbed her from behind, police said. The man fondled the woman as he dragged her backward until she was able to break free and call police, according to police spokeswoman Officer Johnna Watson.

The woman did not know the man, described as 25 to 35 years old, about 5 feet, 4 inches tall and approximately 160 pounds with black hair. He was wearing a gray shirt, black vest and gray sweatpants. His race was not known.

Police are investigating the case as a sexual assault and kidnapping.

Crime Stoppers of Oakland is offering a reward of up to $5,000 for information leading to the man's arrest. Tipsters are asked to call the Youth and Family Services Division at 510-238-3641 or the tip line at 510-637-0298.

David DeBolt covers breaking news. Contact him at 510-262-2728. Follow him at Twitter.com/daviddebolt.