Detectives investigating said the incident happened in the Tullygally Road area at around 5.40pm.
A PSNI spokesperson said: “The 21 year old was walking on the Black Path when he was approached by two unknown males, one of whom produced a knife and the other a screwdriver. They threatened the victim, forcing him to handover his phone, bankcards and cash.
"The pair forced the victim to walk with them to Carrigart and then made off.
"The robbers are described as approximately 16 to 17 years old. One had light brown hair and was wearing a grey fleece tracksuit under a navy Berghaus body warmer and a blue surgical face covering.
"The second was wearing grey fleece tracksuit bottoms and a black top, white baseball cap and a blue surgical face covering.
"Detectives are investigating a possible link between this robbery and an attempted robbery which occurred a short time earlier. A 16 year old boy was walking on Lake Road close to the leisure centre at around 5.10pm when he was approached by two teenagers. One of the boys produced a knife and demanded money. The victim refused and the pair made off.
"Anyone with information regarding either crime is asked to contact detectives by calling 101, quoting references 1650 and 1830 20/03/23.
"Alternatively, information can be provided using the non-emergency reporting form via www.psni.police.uk/makeareport/ .You can also contact Crimestoppers anonymously on 0800 555 111 or online at www.crimestoppers-uk.org/.