A woman was pinned to the ground and held at knifepoint while thieves ransacked her handbag in Worksop.
The 54-year-old victim was making her way home along an unlit footpath between Carlton Road and Queensway, next to the Worksop-Retford railway line, when two men approached and threatened her.
Police have urged a man who may have seen the attack, which happened at around 11.30pm on Tuesday November 6, to contact police.
The man, who was white and dressed in white trousers, was walking towards the footpath on which the victim was attacked.
Detectives think he may have seen the culprits.
The victim's handbag was stolen in the attack, which contained cash, a pink HTC mobile phone and a Kindle.
She also lost a cap from her tooth when she bit her attacker in the struggle.
She was not injured, but was left extremely shaken by the ordeal.
The attackers were white, aged between 16 and 20, and wearing dark clothing.
Detective Constable Ricci Skelton, of Retford CID, said: "If you were the man walking in the area at the time of the attack please get in touch.
"We have increased patrols in the area and would advise people to avoid walking alone in secluded, unlit areas at night. Be vigilant and report any suspicious incidents to the police.
"If you own a Smartphone, activate the 'Find My Phone' app or install a free tracking app, such as PREY. Also, 'secure' your phone by activating and using the PIN code/pattern option.
"Record your IMEI number (find this number by typing *#06# into your mobile phone and it will display this 15-digit number) and record it with a property register, such as www.immobilise.com."
The man in the white trousers, or anyone with any information, should contact DC Ricci Skelton at Retford CID on 101, extension 807 7477, or call Crimestoppers anonymously on 0800 555 111.
