The culprits are still at large after the incidents happened between 11pm and 11.30pm.
Two men are reported to have entered a petrol station on Leads Road shortly after 11pm yesterday and threatened the staff with two weapons.
The men then stole cash and cigarettes and left the scene.
The staff were not physically harmed but were shaken by the incident.
A further incident occurred on a cycle path between Chamberlain Road and Ashendon Drive where a man was threatened by two men with weapons, who stole his mobile phone - a white and gold IPhone 5S with black case - and his pedal cycle. The culprits Man grabbed the man and took him to the ground but he was not injured.
The two men are described as both being white, around 5ft 2/3ins tall, of medium build and in their mid-20s. They spoke with local accents and were both dressed in black.
A Humberside Police spokesperson said: "We would reassure residents that we are doing all we can to investigate both of these incidents and do not want to cause alarm, but are urging residents in the area to be extra vigilant while these individuals are still at large.
"We are providing extra police officers in the area this evening and would ask if anyone sees anything suspicious to call 999."
Anyone with information is asked to call 101, quoting log 696 22/04/2017. People can also call Crimestoppers anonymously on 0800 555 111.