According to police facts before the court, Mitch Bleimuth, 18, of Osborne Parade, was with a small group of young men partying in the garage of a house in Fleetwood Cres, Warilla, when a fight began about 11pm.

It is alleged that when one of the victims - a 17-year-old - tried to intervene, he felt two "punches" to his back and when he turned around saw Bleimuth standing behind him.

The victim did not realise he had been stabbed until another party-goer alerted him.

Soon after the first alleged attack, a 16-year-old youth felt a single "punch" to his lower back and when he withdrew his hand from the area where he had felt pain, there was blood on his fingers. He turned around and saw Bleimuth standing behind him.

Both victims were taken to hospital suffering deep lacerations which required many stitches.

Police who searched the scene found a broken and a bloodstained piece of glass they will allege was used in the attacks.

Opposing bail, Police Prosecutor Sergeant David Ross said the two teenagers were victims of extreme violence and police had serious concerns for their safety and the public at large if Bleimuth was granted his freedom.

Sgt Ross said the accused was known to police and there were serious concerns he would offend again.

"He knew the victims well and he stabbed them with a piece of glass," Sgt Ross said.

Magistrate Pearce said while the charges were very serious, bail should not be used as punishment.

He granted Bleimuth bail on the condition an acceptable person lodged a $5000 cash surety, that he reports to police daily, does not approach the alleged victims, and accepts a 7pm to 6am home curfew.

"Any breach of the bail and he's to be arrested," Mr Pearce said.

The matter was adjourned to Wollongong Local Court on March 16.