Tsvangirai's spokesman, William Bango told the BBC a scheduled court appearance was canceled because of the man's injuries and that he was in intensive care. Bango said after reviewing scans and X-rays, doctors were concerned Tsvangirai had a fractured skull. He also received two pints of blood overnight, Bango said.
Tsvangirai was one of 50 people arrested at a demonstration Sunday, which President Robert Mugabe's government has banned.
No one was allowed to see the arrested people until Tuesday during a first court appearance, where many of them were bloodied, wearing bandages and limping, the report said.
A member of Tsvangirai's Movement for Democratic Change party, Tendai Biti said he witnessed the police beating.
"There was a time when for 15 minutes they were assaulting him with their baton sticks non-stop. He must have passed out at least three times," Biti said.
Mugabe's government has come under numerous international condemnations for the rally violence, in which one protester was killed.