Security at UK mosques is to be discussed following the terror attacks in New Zealand that left 49 dead.
Senior counter-terrorism experts and security services will hold talks with the home secretary later on how mosques in the UK can best be protected.
Police are also stepping up patrols around mosques to provide reassurance.
The Queen said she is “deeply saddened” by the shootings at two Christchurch mosques, with condolences also paid by Prime Minister Theresa May.
‘Horrifying terrorist attack’
The Queen said: “Prince Philip and I send our condolences to the families and friends of those who have lost their lives.
“I also pay tribute to the emergency services and volunteers who are providing support to those who have been injured.”
She added that her “thoughts and prayers are with all New Zealanders” at this “tragic time”.
Other members of the Royal Family have also offered their condolences.
The Duke and Duchess of Cambridge, in a joint message with the Duke and Duchess of Sussex, called the attack “senseless”. They ended the message with the Māori words Kia Kaha, meaning “stay strong”.
Mrs May described what happened as a “horrifying terrorist attack”, adding: “My thoughts are with all of those affected by this sickening act of violence.”
The attacks in Christchurch on Friday, the deadliest in New Zealand’s history, happened at around the time people were attending the mosques for prayers.
At least 20 people have also been wounded in what the country’s prime minister Jacinda Arden described as one of the nation’s “darkest days”.
Scottish First Minister Nicola Sturgeon is planning to visit Glasgow Central Mosque on Friday, and said the events in New Zealand “will feel very personal and close to home” for Muslims.
MPs have observed a minute’s silence in the House of Commons and flags over Downing Street are to be flown at half-mast.
British security minister Ben Wallace called the attack “repugnant” and said the UK “stands shoulder to shoulder with New Zealand against terrorism”.
He said he and Home Secretary Sajid Javid would meet police counter-terrorism chiefs and the security services later on Friday, “to discuss what further measures we can take to protect our mosques and our communities from any threats here in the United Kingdom”.
Mr Wallace added: “Our police and security services treat all threats the same and all terrorists the same no matter what communities, religion or background they come from. A terrorist is a terrorist and we shall deal with them exactly the same.”
More police at mosques
Mayor of London Sadiq Khan described the attacks as “heartbreaking”.
He said that, after discussions with Scotland Yard, there would be “highly visible policing around mosques today, as well as armed response officers, as Londoners go to pray”.
Met Police Assistant Commissioner Mr Basu, the national policing lead for counter-terrorism, said that as well as the “reassurance patrols”, there would be increased “engagement with communities of all faiths, giving advice on how people and places can protect themselves”.
Police Scotland and Greater Manchester Police also said patrols would be increased around mosques, but added there was no intelligence to suggest there was a specific threat.
Greater Manchester Police said “we know all too well the effects of terrorism”.
Meanwhile, Met Chief Superintendent Nick Aldworth, who leads the government’s counter-terrorism strategy, told BBC 5 Live that police would be assessing what impact the Christchurch attack could have on Britain.
“There’s no doubt in my mind, that having seen what I’ve seen here, this is something that we within counter-terrorism should be responding to in the UK and ensuring our current plans and thinking is correct,” he said.
‘Be more vigilant’
The East London Mosque and London Muslim Centre said its thoughts and prayers were with the victims, and urged its community to “be more vigilant than ever”.
Meanwhile, Finsbury Park Mosque, whose worshippers were targeted in a terror attack in June 2017, shared a picture of flowers and a note of support which it had received from members of the local community.
Sir Mark Rowley, the UK’s former head of counter terrorism at the Met Police until last year, told BBC Radio 4’s Today programme that although “Western societies have always had racist thugs” who commit crimes, in recent years they have become “more organised and with more terrorist ambitions”.
He said he thought social media was “a very big problem” by helping conspiracy theories flourish.
Downing Street and Home Secretary Sajid Javid also criticised social media, saying Facebook, Twitter and YouTube should have been quicker to remove video footage – which had been recorded by the gunman during the attack – from its platforms.