Serial killer Peter Tobin "definitely killed others" according to a former police officer who worked on the case.

The "sadistic, evil" murderer, who buried two of his three victims in a back garden in Margate, is now being urged to confess to other crimes.

The fresh appeal is being made by former detective superintendent David Swindle, who said: "I would like to think that some day you will have the humanity and respect to admit everything you have done."

Tobin, now 70, is serving life sentences for the murders of Polish student Angelika Kluk, Scottish schoolgirl Vicky Hamilton, 15, and Dinah McNicol, 18, from Tillingham, Essex.

He was convicted of 23-year-old Ms Kluk's murder in 2007.

Police then followed a trail of clues to the garden in Irvine Drive, Margate, where they discovered the remains of missing teenagers Ms Hamilton and Ms McNicol.

He was convicted of their murders in 2008 and 2009.

In an interview with the Mail on Sunday, Mr Swindle - who led Operation Anagram in the aftermath of Ms Kluk's murder - said: "There are definitely other people Tobin has killed and only he knows who they are.

"Tobin was a sadistic killer who was determined to take lives and conceal them for his pleasure.

"Ten years on from the murder of Angelika Kluk, it's a poignant time for the families.

"You should never give up, that was my attitude. Push, push, push and get the truth. I still think of Tobin a lot, particularly at this time of year.

"You should never forget the victims and you should never forget the evil killers who hold the key to the victims.

"I live in hope that some day we will get the truth about what Tobin has done."