She tried to run past them but one of the men grabbed her by the clothing and another man began pushing her.
They pushed her towards a creek and she fell over but managed to fight back as the two men struggled with her.
She managed to break free and ran away.
Two young men then fled.
The victim ran back to her friends. They then left the park and called police from home.
"We really need to speak to the third young man who witnessed the initial assault before the victim was pushed towards the creek," Detective Senior Sergeant Glenn Baldwin said.
"We believe this was a sexually motivated attack and this young man can help us.
"He is a witness and we need him to come forward and help us."
Detectives have been out in the area this morning gathering and reviewing CCTV footage, but would like to hear from anyone who was in the park last night and saw the group of young men.
Officers will be at the park around 8.30pm tonight, looking to speak to regular park users who may have seen something.
Anyone with information is asked to contact Auckland City Police Crime Squad on (09) 302 6557.
The three men are described as:
First man:
• Male Caucasian
• Aged 16-17 years old
• Dark hair
• Wearing long beige-coloured chinos, hooded sweatshirt and jandals
Second man:
• Male Caucasian
• Aged 16-17 years old
• Wearing beige-coloured shorts, hoodie, jandals
Third man:
• Male Caucasian
• Aged 16-17 years old
• Denim shorts, black or dark-coloured T-shirt
