A South Auckland man sprang from the bushes of the Manurewa botanical gardens on Valentines Day before viciously attacking and indecently assaulting two 15-year-old girls.

Amandeep Singh, 21, pleaded guilty in the High Court at Auckland this morning to indecent assault and assaulting a female.

Court documents detailed the random attack, saying about 6.30pm on February 14, the teenagers were walking along a bush track in the gardens.

Singh, a slightly built Indian man, was standing in the bushes and as the girls walked past he called out: "Are you girls tired?"

They replied "yes" and kept walking.

Singh came out of the bushes and grabbed one of the girl's bottoms.

Scared, the girls kept walking faster but Singh followed them, calling out "I thought you girls were tired".

He chased the girls down and grabbed one of them. A tug-of-war ensued with one girl trying to pull her friend away by one arm and Singh pulling on the other.

He then swung a punch at the friend who ran to get help.

Singh threw the remaining girl to the ground and sexually assaulted her while kissing and licking her face.

He covered her mouth so she could not scream, bit her on the cheek and punched her when she struggled.

At one stage the girl managed to get up but Singh blocked her exit by opening his arms and yelling "come here".

She finally managed to run away.

Singh remained in the bushes holding her jumper and yelled after her: "You better run before I hurt you."

Police said both complainants were "very shaken" by the incident.

Singh initially told police the girls attacked him and he had to defend himself to get away.

However, he changed his plea to guilty today.

Justice Timothy Brewer issued a "three strikes" warning and remanded him in custody until sentencing on October 19.

- © Fairfax NZ News