U.K. police said Monday they had arrested two teenagers after the latest arson attack on sites including Jewish ones in London, bringing the number of arrests for six incidents to 15.

Matt Jukes, deputy commissioner of the Metropolitan Police, said the new arrests came amid a pattern of ¡°thugs for hire¡± as the United Kingdom sees ¡°the pressure of hostile states bearing into our communities.¡±

In parliament, Security Minister Dan Jarvis denounced violence against British Jews as ¡°an attack on all of us,¡± pledging to ¡°do whatever it takes to stop the cowards and the thugs who seek to intimidate our Jewish communities.¡±

London¡¯s police force has been probing whether the attacks have been instigated by Iranian proxies, as Britain¡¯s chief rabbi warned of ¡°a sustained campaign of violence and intimidation¡± against Jews in the U.K.

¡°For anyone tempted by offers of financial reward from foreign states to conduct hostile acts against the U.K., my advice and my message is unambiguous: you will be discovered, and the consequences will be severe,¡± Jarvis said in parliament.

In the latest incident late Saturday, a bottle containing ¡°some sort of accelerant¡± was thrown through a window of Kenton United Synagogue in Harrow, northwest London, according to police.

Smoke was seen inside the room, but no injuries were reported, police said.

Two males, aged 17 and 19, were arrested overnight and remain in custody.

Jukes told BBC radio there had now been 15 arrests following six separate incidents on premises including a Jewish-led ambulance service and a Persian-language media outlet.

He added the possible involvement of proxies was ¡°a very serious line of inquiry.¡±

¡°We¡¯ve seen a pattern with other actors of thugs for hire ¡ª people taking cash. It looks like quick and easy money,¡± Jukes said, noting convictions last year in a case involving individuals working for Russia¡¯s Wagner Group.

¡°This is part of the modern hybrid war fought by proxies,¡± he added.

¡°We clearly see the pressure of hostile states bearing into our communities, and policing is going to respond to that.¡±

A little-known group, Harakat Ashab al-Yamin al-Islamiya, which has links to Iran, has claimed responsibility for many of the recent attacks, according to SITE Intelligence Group.

As concern over the spate of attacks intensified, Chief Rabbi Ephraim Mirvis said in a post on X that ¡°a sustained campaign of violence and intimidation against the Jewish community of the U.K. is gathering momentum.¡±

¡°Thank God, no lives have been lost, but we cannot, and must not, wait for that to change before we understand just how dangerous this moment is for all of our society,¡± he added.