The first assault happened in the Newtownabbey area of North Belfast shortly after 9pm, in a house on the Whitewell road.
One man has been arrested and is being questioned by the PSNI.
The second assault happened in Derry at 10.30pm last night, when a teenage girl was approached by a man in a public park.
Police are investigating and say the girl was severely traumatised by the ordeal.