The young woman was attacked and raped in an alleyway near Catherine Street in Limavady, a market town in County Londonderry.
The police were not able to arrest the attacker and have asked people who witnessed the attack to contact officers.
This comes as tens of thousands of police officers and military soldiers have been deployed in the UK capital to fight what British officials call potential terrorist threats.
Tight security measures are being taken for the London Olympics with 12,500 police officers and 18,200 military troops being deployed in London.
Prior to the start of the Olympic Games, concerns were raised over the British officials’ obsession with what they called counter-terror security measures. Critics argued such obsession would lead to a rise in crimes.
The latest news about the woman being attacked and raped in County Londonderry comes as critics say, with all the security measures taken, London is more like a city preparing for war than an international peaceful event.
ISH/MA/HE