A man has been arrested over an alleged random, daylight attack on a couple in Melbourne CBD that left one with a broken eye socket.

Claude and Emma Bennett told 9News they thought they were going to die when they were unexpectedly set upon by a man and a woman near the Flinders Street Station underpass about 1pm on March 28.

Police arrested a 37-year-old man near foreshore in McRae, about 88km from the scene of the crime, over the attack this morning.

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But they are still looking for a woman who was also allegedly involved in the attack.

Claude, 60, was allegedly thrown and pinned to the ground, then repeatedly punched and kicked in the face before his wife was targeted.

"He punched me in the face, grabbed me, shoved me, threw me… and everything else was a bit of a blur," Emma told 9News.

Detectives said the "atrocious" assault on the disability support workers, who were simply walking to lunch, was completely unprovoked.

"I can only describe it as vicious, violent and brutal," Detective Senior Sergeant Andrew Eyries said.

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