Police chiefs today released the first CCTV footage of murdered prostitute Anneli Alderton, taken a week before her body was discovered last Sunday.The images were taken on board the 5.

Police chiefs today released the first CCTV footage of murdered prostitute Anneli Alderton, taken a week before her body was discovered last Sunday. The images were taken on board the 5.53pm train from Harwich to Colchester on Sunday December 3.

Both stills released by the police show the 24-year-old's platinum blonde hair scraped back into a pony tail and show her wearing a black jacket with a furred hood round it.

It was also revealed that Miss Alderton was three months pregnant, but detectives said her condition was not thought relevant to the investigation.

Det Chief Supt Stewart Gull, leading the investigation into the Ipswich serial killer, said: “The images for the first time give us a clear indication of what she was wearing on December 3.”

Along with the black jacket Anneli was wearing a grey top, blue jeans and white footwear. She was also carrying a shiny nylon shoulder bag, closed with a cord.

“We now need to piece together Anneli's movements after this image was captured,” said Mr Gull. “At what station did Anneli get off the train? And where did she go after that?

“I would ask people to look carefully at the images. If anyone saw Anneli after the evening of December 3, we want to hear from them.”

At a press conference this morning Mr Gull said that officers were looking at mobile phone calls made and received by the girls and were also analysing DNA, but refused to go into more detail.

He said: “I won't go as far as to say the net is closing in but we are making good progress. It's been a challenge this week as you could imagine.

“One murder inquiry presents a challenge - we were already dealing with two murders and then another three from Sunday, and that presents a significant challenge.

“Time has moved on and officers are still arriving to help with the investigation. We've had about 9,000 calls from the public. All of this presents a challenge but we are making good progress.”

About 350 officers and staff from forces as far away as Northern Ireland are now in Suffolk assisting with the investigations.

Mr Gull said detectives were looking at “a number of interesting people” and pursuing “a number of interesting lines of inquiry”, which included talking to many of the 400 sex offenders registered in Suffolk.

He said police had spoken to the driver of a blue BMW, linked in the media to the murders, and had not ruled him out of the investigation - though he had not been interviewed as a suspect.

Any women's clothing found in Ipswich should be reported so that police could “seize it and secure it” - with forensic evidence likely to play a key role in eventually tracking down the killer.

When asked about Anneli and the other women's mobile phone records, Mr Gull said: “I don't want to go into details, it's very sensitive, but it's something we're looking at.”

The town's prostitutes remain a significant source of information and the police chief said it would be difficult to crack the case without their continued help.

Mr Gull repeated appeals for anyone with information, no matter how inconsequential they might believe it to be, to call the inquiry's hotline on 0800 096 1011.

t A minute's silence was observed by around 25,000 football fans this afternoon at Portman Road, before Ipswich Town's game with Leeds United. The Right Reverend Richard Lewis, Bishop of St Edmundsbury and Ipswich, said prayers for the murdered women. Announcements were made over the public address system for anyone with information about the murders to come forward. Spectators were also given leaflets about personal safety as they entered the ground - which is situated near Ipswich's red-light district.