Mr Hassan, 17, who came to the the UK from Somalia when he was two years old, was pronounced dead when officers arrived in Bartholomew Road in the Kentish Town area of Camden at about 8.30pm.
Police believe he was attacked nearby before managing to stagger out into Bartholomew Road.
His uncle, Yusuf Ahmed, said he was a "good guy" who was "always smiling" and enjoyed playing football with his friends as well as helping his mother.
And his aunt, Fatima Deria, speaking on behalf of his mother, said: "She said she came here for their safety, to flee from home. But he's not safe, is he? He's dead. This is where he lost his life, not back home."
Less than two hours later, at 10.15pm, officers responded to another call on Malden Road - a short bus ride away from where the first attack took place - after neighbours heard "a lot of screaming" outside.
There they found Mr Mohamed, 20, with serious stab wounds. He was also pronounced dead at the scene, and it is believed he and his friend were chased by four men.
His friend escaped uninjured and the suspects fled along Malden Road towards Prince of Wales Road.
The deaths came after an earlier stabbing in the borough at about 8pm.
Officers on patrol were pursuing a silver Mercedes in Eversholt Street when a member of the public alerted them to an incident outside a block of flats in nearby Aldenham Street.
There they found a 16-year-old boy who had been stabbed, and he continues to recover from non-life threatening injuries at a local hospital.
Police are continuing to appeal for witnesses - or anyone who may have useful information - to come forward.
Detective Chief Inspector Paul Considine, leading the investigation, said: "What is clear is that there were three violent attacks, by a group of men armed with knives, within about two hours of each other and within about a mile of each other.
"I need the public's help to establish the exact circumstances in which two young men were murdered and another seriously injured, and to identify the people responsible.
"Today, I am asking local residents or those people who were out in the area that night to think back - and if they saw something that may help us, please get in contact.
"I can understand why some people may be reluctant or nervous about coming forward but we need your help. We will treat your information in the strictest of confidence."
Police found Lewis Blackman, 19, of Camden, with knife wounds at about 3.20am on Sunday.
Mayor Sadiq Khan has been under pressure to do more to combat deadly knife crime in London, as have the courts, with a top Scotland Yard officer calling for tougher sentences and better rehabilitation to stop youngsters from reoffending.
A number of murder probes have been launched into fatal stabbings since then and Detective Chief Inspector Considine said the frequency of fatal stabbings in the capital was "shocking".
He continued: "We all have a part to play in preventing this. If you know something about these murders then please do your part in helping us with this investigation.
"One line of enquiry that we are urgently pursuing is that a blue van was seen in the area of the two murders.