Two teenagers and a man in his 30s have been killed after five separate attacks in London over a 24-hour period.

Police have arrested a total of 14 people following the unlinked attacks in east and south London in a wave of violence that began on Friday afternoon.

None of the attacks is believed to be linked, but the pressure of dealing with so many incidents has put Metropolitan police officers under pressure, Sadiq Khan, London’s mayor, has said.

He expressed his disgust and said the force was working at its limit. “I am sickened to hear that two young lives have been ended within minutes of each other … Our overstretched police are working around the clock to keep Londoners safe. They need our support to end this scourge of violence.”

Donald Trump, the US president, used the murders to attack Khan, renewing the antipathy between the two men. He retweeted a post by hard-right commentator Katie Hopkins about the killings, saying: “LONDON needs a new mayor ASAP. Khan is a disaster – will only get worse!”

A spokesman for the mayor said he was “focusing on supporting London’s communities” and was “not going to waste his time responding to this sort of tweet”.

The first attack happened at 4.42pm on Friday in Wandsworth, south-west London, when an 18-year-old was stabbed in Deeside Road. Six males aged between 16 and 19 were arrested on suspicion of murder.

Just 12 minutes later, a 19-year-old man was shot dead in Plumstead, in the south-east of the capital , 13 miles away. Police have arrested three boys aged between 16 and 17, and a 17-year-old girl on suspicion of murder.

Then, at 3.22am on Saturday, two men were slashed and stabbed in a fight near Clapham North underground station. Four men were arrested, two for violent disorder, one for carrying a bladed instrument and another for possession of a stun gun.

The fourth attack happened at 4am, after a fight at a pub in Brixton, where one man was stabbed and injured.

Then just before 2pm a man in his 30s was stabbed to death in Alton Street, Tower Hamlets, in a field near a nursery and a mosque.

Scotland Yard said residents in both areas could expect to see a heightened police presence as detectives from the Met’s homicide and major crime command investigated.

My heart goes out to the family of this victim after this absolutely tragic incident.



I spoke at length with people on the Aboyne Estate tonight, anyone with concerns can contact me - I’m here to listen.



Sending love to the Tooting family tonight - this is heartbreaking ❤️ https://t.co/6MD4r6fDUN — Dr Rosena Allin-Khan (@DrRosena) June 14, 2019

The Tooting Labour MP, Rosena Allin-Khan, in whose constituency the killing took place, said the Wandsworth killing was heartbreaking. “My heart goes out to the family of this victim after this absolutely tragic incident,” she tweeted. “I spoke at length with people on the Aboyne Estate tonight, anyone with concerns can contact me – I’m here to listen. ”

In April it emerged that homicides in England and Wales reached their highest level in a decade, with a third of all knife offences recorded in London. Nationally, instances of knife crime rose by 6% on the previous year, although the Office for National Statistics said the use of bladed weapons was concentrated in urban areas, though there were some signs the increase was slowing.

The ONS figures said there had been a 2% rise in instances of firearm offences in the year.

The Met appealed to the public for information. “The police cannot solve this problem alone,” a spokesman said. “Communities have a vital role to play in tackling violent crime. We want to hear from anyone who may have information about people who may carry knives or firearms, or who are involved in organised drug crime and violence.”

Speaking at a conference on Saturday in central London on gun and knife crime, the father of murdered schoolboy Damilola Taylor said young people still have still not learned lessons from his son’s death.

Richard Taylor called on politicians to engage with communities to tackle youth violence in the capital.

“Young people haven’t really learned the lessons of the death of Damilola, of Stephen Lawrence, and several others; they have taken life as if it’s something to play with,” he said.

“In our work in the past 15 years at the Damilola Taylor Trust, we have found that the problem that underpins the continuous surge in knife crime in the city of London is based on issues around family neglect.

“The family issue has often contributed to young people being neglected from home as a result of a … in dysfunctional home[s].

“Secondly, part of the discussion that has been emphasised here is that the problem starts in schools as a result of the schools [them] not understanding the background of these children.”

Damilola was found bleeding to death in a stairwell near his home in Peckham, south London, after being stabbed in the leg with a broken beer bottle by a gang of youths in 2000.