A sex attacker who preyed on a 68-year-old woman in a secluded alley could strike again, police said today.

Extra officers have been called in to patrol Rottingdean, near Brighton.

The victim's ordeal lasted several minutes and left her traumatised.

At a Press conference today, Detective Inspector Paul Fullwood, heading the inquiry, described the assault as "sickening".

He declined to give details of the attack other than to say it was being classed as a serious sexual assault.

Police believe the attacker is local and deliberately picked a quiet lane for a premeditated attack.

He lay in wait in the dark at 7.40pm on Saturday as the pensioner walked through The Twitten, which links Steyning Road and Marine Drive.

She heard running footsteps behind her and moved aside but the man came up behind her and grabbed her.

After the attack he ducked through a gap in picket fencing and ran across school playing fields to Newlands Road.

Mr Fullwood said the victim was physically unhurt but mentally traumatised. He said: "She is a very strong person but this has really knocked her for six."

Mr Fullwood added: "We are concerned this man may strike again so it is vitally important we trace him."

As officers were carrying out house-to-house inquiries today, Mr Fullwood appealed for witnesses to come forward.

The offender was 5ft 6in tall with a soft voice and smelt of alcohol. Police say he clearly knew the area.

They are keen to trace two women the victim saw near Our Lady of Lourdes on the corner of Whiteway Lane and a man wearing a pale blue or grey casual top, pale trousers and with light-coloured hair.

Mr Fullwood said: "This attacker clearly had been drinking and we want to hear from anyone who may have seen him in a pub, off-licence or at a private function."

Police said there was no connection with another attack at 3.50am yesterday, when a woman was pushed over and assaulted as she walked home through the Elm Grove area of Brighton.

Her attacker fled towards Lewes Road.

He is described as of Mediterranean appearance, 5ft 10in tall, between 22 and 30 and with collar-length wavy dark hair.