A 15-year-old boy is described as being in a serious condition in hospital after being repeatedly stabbed.
The attack took place in Woodman Path, Hainault, just before 7pm on Monday.
Police said he was slashed multiple times in the upper body, but his injuries are not thought to be life-threatening.
Three teenage boys from Hainault, two aged 16 and one aged 14, were arrested overnight following investigations by police.
A Metropolitan Police spokesman said: “They remain in custody at various east London police stations.
“Anyone with information is asked to contact Redbridge CID via the 101 number or call Crimestoppers anonymously on 0800 555 111.”
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here