A man's been arrested following a violent sexual assault in Dublin's north inner city. 

This horrific attack took place at around 3am on Monday in an alleyway at Parnell Place.

It's understood the alarm was raised when concerned residents heard a woman screaming.

Gardai arrived on the scene while the victim was still being assaulted.

She was taken to the Sexual Assault Treatment Unit in the Rotunda.

A man in his 30s was arrested but became ill and had to be brought to the Mater for treatment.

It means his period of detention has been delayed.