Seventeen people have been arrested across south London amid alleged "rising tensions" after the Oxford Street stabbing of 18-year-old Seydou Diarrassouba on Boxing Day.

Police found evidence of potential follow-up attacks on social networking sites and subsequently raided at least 20 addresses in Wandsworth, Merton, Southwark and Westminster on Friday, December 30, - the targets are believed to be associated with gangs.

Diarrassouba, who attended South Thames College and lived in Mitcham, died from a single stab wound to the heart after collapsing near Bond Street Tube station in front of horrified shoppers.

Eleven people, aged between 16 and 22, were arrested at the scene and were given police bail until mid-January - another 13 were arrested as part of the raids for offences including GBH, robbery, affray, intent to supply drugs and burglary.

On Saturday, following the raids, murder detectives announced they had arrested three people, two 16-year-olds and a 20-year-old, on suspicion of Mr Diarrassouba's murder.

Commander Mak Chishty said: "We were aware of rising tensions in the wake of the murder and having monitored the situation closely, including various comments that have been made on social networking sites.

"We felt it vital we take robust and prompt action in order to pre-empt any potential future violence."

Earlier this month, Mr Diarrassouba appeared in court charged with robbery and assault, after allegedly stealing a Blackberry smartphone in Clapham in September. He was due to stand trial over the charges this month.

This week the teenager's family have issued a statement this week in order to appeal to potential witnesses.

His family said: "Our loving son and brother has been snatched away from us. A simple shopping trip has turned into a complete nightmare for our whole family.

"We are urging anyone who was in Oxford Street at the time of the incident to come forward with any evidence, no matter how little relevance they think it could have, to help the police with their ongoing investigation.

"Whoever took his life took our backbone away. Seydou kept us upright and now we feel weak as we have lost a very special part of us."

Anyone with information should contact the incident room in Hendon on 020 8358 0100 or speak anonymously to Crimestoppers on 0800 555 111.