Imam Mohammed Mahmoud told reporters Monday that he and "other brothers" were able to prevent onlookers from beating up the suspect and held him until police arrived.
London's police commander says the van attack near Finsbury Park Mosque was clearly an attack on Muslims.
In a statement, they said: "We are co-operating fully with the Metropolitan Police investigation and our thoughts are with those who have been injured in this cowardly attack".
Mr Osborne was arrested on suspicion of attempted murder and alleged terror offences.
The Muslim Council of Britain said the latest terrorist attack in London was the most violent manifestation of Islamophobia in Britain in recent months, and called for extra security at places of worship.
Van plows into crowd near London Finsbury Park mosque, killing one
Witnesses described hearing the man, who was detained by members of the public at the scene, shout: "I'm going to kill Muslims". Khadijeh Sherizi, who lives next door to Osborne, said: "I saw him on the news and I thought "oh my God" that is my neighbour.
Eyewitness Abdul Rahman told the BBC that the driver of the van said that he wanted to "kill all Muslims".
Mayor Sadiq Khan, London's first Muslim mayor, implored the city's residents to show solidarity.
Police said the 48-year-old man who was driving the van has been arrested and taken to a hospital as a precaution. On May 22, a suicide attack killed 22 people and injured almost 60 after an Ariana Grande concert in Manchester.
British authorities, including Prime Minister Theresa May, and Islamic leaders moved swiftly to ease concerns in the Muslim community following the attack shortly after midnight that injured at least nine people in London's Finsbury Park neighborhood, which is home to a large Muslim population.
The attack was, she said, "a reminder that terrorism, extremism and hatred take many forms and our determination to tackle them must be the same, whoever is responsible". People surrounded the driver and witnesses said the outraged crowd began attacking him. That incident, plus the four attacks, have stretched British authorities and left May's government, which suffered losses in a snap election, reeling. It is too early to state if his death was a result of this attack.
Sarfraz Ahmed thanks nation for support
Arthur, like others, also want that cricket loving fans in Pakistan, get to see their heroes play worldwide matches . Their head coach, Mickey Arthur, hoped this performance would lift the country. "It has been an up and down ride".
The scene is just metres from the main railway line linking London with Edinburgh, the main Arsenal Football Club shop and what was the Rainbow Theatre, considered the prestige London concert venue in the 1960s and 1970s.
May chaired an emergency response meeting Monday morning.
"Sending love and prayers to the victims in #FinsburyPark London".
"I saw so many of them crying, screaming, trying to get the police and the ambulance", she said.
Britain's terror alert level is at "severe", meaning security officials believe an attack is highly likely.
Otto Warmbier, US student freed from North Korea, has died
Fred Warmbier told Fox News' Tucker Carlson on Wednesday from his OH home that his son, Otto , "is not in great shape right now". Ambassador to the United Nations Bill Richardson said he was saddened and angry about the death of the American college student.
Earlier this month, a van veered into pedestrians on London Bridge, setting off vehicle and knife attacks that killed eight people and wounded many others on the bridge and in the nearby Borough Market area.
- In final hours before vote, Handel reflects on 'craziest' 6th District race
- Mike Pence Hired a Personal Lawyer to Handle the Russia Investigation
- Bihar Governor Ramnath Kovind is NDA's Presidential nominee: Amit Shah
- US student who was returned from North Korea in coma has died
- 'Happy' that Bihar Governor is Presidential nominee: Nitish Kumar
- Portugal: more than 20 dead in forest fires
- Trump offers assistance to United Kingdom after London Finsbury Park terror attack
- House leader joins Handel on final campaign day
- ASCO 2017: Genomic Sequencing Approach Step Toward Early Cancer Detection
- New Brand—Endless Opportunities