Man, 21, charged over Sydney park assault

A 21-year-old man is due to face court after he allegedly punched a 51-year-old woman several times in the face then sexually assaulted her in southwest Sydney.

Police allege the victim noticed a man watching her as she walked along a track in Liverpool's Lighthorse Park shortly before midnight on November 11 before he attacked.

She screamed and the alleged offender was chased by people nearby however they eventually lost sight of him.

The woman was taken to Liverpool Hospital with facial injuries including cuts, bruises and damage to her teeth.

Police since arrested the alleged attacker in Warwick Farm, charging him with aggravated sexual assault - inflict actual bodily harm on victim.

He was refused bail and is due before Parramatta Local Court on Saturday.