A 17-year-old boy has pleaded guilty to arson not endangering life after an attack on a synagogue in north-west London on Saturday night.
The plea on Tuesday came as seven people were arrested over an alleged separate plan to commit an arson attack targeting the Jewish community, the Metropolitan Police said.
The teenager, a British national from Brent who cannot be named for legal reasons, was arrested by the Met Police on Sunday after a bottle containing a type of accelerant was thrown through the window of Kenton United Synagogue on Shaftesbury Avenue, Kenton, on Saturday night.
Minor damage was caused to the building and no-one was injured.
Jewish charity the Community Security Trust said the attack on Kenton United Synagogue caused minor smoke damage to an internal room but there was no significant structural damage.
At Westminster Magistrates' Court, District Judge Nina Tempia freed the teenager on bail with conditions including to live and sleep at his home address and to not enter any synagogue.
He is scheduled to appear at Willesden Youth Court on 4 June.
Deputy Assistant Commissioner Vicki Evans, the senior national co-ordinator of Counter Terrorism Policing, said: "This is a significant development, being the first conviction in relation to one of the recent spate of arson attacks on Jewish, Israeli or Iranian-linked venues.
"We've made very clear that we will be relentless in our pursuit of anyone involved in carrying out or planning these arson attacks."
A 19-year-old man who was also arrested after the attack was released on bail pending further inquiries, the Met said.
Since late March, there have been a series of arson attacks, including Jewish community ambulances that were targeted in Golders Green, two synagogues and a former Jewish charity. Another incident involved a drone which was flown near the Israeli embassy.
Officers from Counter Terrorism Policing London said on Tuesday they had arrested three men aged 24, 25 and 26 in Harpenden, Hertfordshire, on Sunday, over an alleged plan to commit an arson attack targeting the Jewish community.
The specific target or venue was not known, the force said.
The men were later released on police bail.
On Monday, a 25-year-old man was arrested in Stevenage, while a 26-year-old man and two women aged 50 and 59 were arrested in a car in Birmingham. They remain in custody at a London police station.
Separately, a 39-year-old man was arrested in Ealing on Tuesday under the Terrorism Act, in connection with an investigation into jars of a non-hazardous substance found in Kensington Gardens on 17 April. He remains in custody.
Officers have arrested a total of 23 individuals since the first attack on a place linked to Jewish communities, or those who oppose the Iranian regime.
Evans added that officers were investigating a "key line of inquiry" into the use of criminal proxies - people being paid money to carry out arson attacks.
She said: "While our investigations into this are still ongoing, my message to anyone even considering getting involved in this type of activity is this: the stakes are high and it is absolutely not worth the risk."
On Tuesday, Prime Minister Sir Keir Starmer said the government "won't relent in our fight against antisemitism and terror".
Metropolitan Police Commissioner Sir Mark Rowley told the BBC that it was currently "very intimidating for British Jews living in London".
He described the incidents as an "intimidatory series of attacks" and said "the whole of society should be as outraged at that as we would be on attacks on any other group because of their race or faith".
Sir Mark added: "We've been putting hundreds of extra patrols around synagogues - that's helped identify one of the attacks early - and putting that protection in place, as well as chasing down those committing other hate crimes."
The spate of attacks has increased fears about antisemitism in the Jewish community, a report by BBC Panorama has found.
More than a dozen Jewish people from a range of UK Jewish communities spoke to Panorama - including an NHS midwife, a student and a musician who was kidnapped - who described a rising undercurrent of antisemitism across society.
Police and policy experts tasked with tackling antisemitism believe this has helped create the conditions for the most serious anti-Jewish hate crimes in recent British history, including the Manchester synagogue attack that left two men dead.
"I think that hatred in the public sphere towards Jews has made them more acceptable as a target for terrorism," Jonathan Hall KC, the government's independent reviewer of terror legislation, told Panorama.
A recent survey by the Institute for Jewish Policy Research, shared exclusively with Panorama, suggested antisemitism was pushing about one in five British Jews to think about leaving the UK.
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