Detectives are investigating five robberies that occurred overnight on Sunday - two of which were in Hyndburn.
Two men pushed a 22-year-old man against the wall and stole his phone then fled as he walked home alone along Cambridge Street, Accrington.
The incident happened at the junction of the alleyway to Water Street and Sultan Street at approximately 11.10pm on Sunday, September 2.
A short time later, at around 12:05am on Monday, September 3, a 20-year-old man was threatened by two men armed with a small knife as he walked home along Hyndburn Road in Great Hawrood.
They got out of a car at traffic lights before approaching him stealing cash and his chain from around his neck.
Detective Inspector Marie Haworth said three other street robberies took place in Padiham shortly after the incidents in Hyndburn.
A 70-year-old man, two 18-year-old men and two teenage boys and a girl were all victims to robberies by two men.
DI Haworth thinks the incidents could be linked and is appealing for more information.
She said: "We are still at the early stages of the investigation and although it is too early to tell whether these incidents are definitely linked, we are considering that possibility.
"Fortunately, none of the victims were seriously injured but were all left extremely shaken by their ordeal and so I would urge anyone with any information to come forward and contact us as soon as possible."
In each of the cases, the men have been described as white, in their early twenties, wearing blacked hooded tops and black shorts, possibly with motifs on the front and black training shoes/boots.
A 25-year-old man from Nelson has been arrested on suspicion of conspiracy to commit robbery and is currently in custody.
Anyone with information can contact police by calling the new non-emergency number 101. Alternatively, information can be passed via the independent charity Crimestoppers on 0800 555 111.