The Community Security Trust has advised the Jewish community to remain “calm and vigilant” following the terror attack in Westminster.
A spokesman said CST had been in close contact with the Metropolitan Police after the incident which took place around 3pm.
There is not believed to be any immediate threat to the community.
“We ask the Jewish community to be calm, vigilant and to co-operate with security measures,” the spokesman said.
A spokesman said CST had been in close contact with the Metropolitan Police after the incident, which took place around 3pm.
The organisation has asked groups from the Jewish community planning trips to central London, "especially... schools", to inform them "as soon as possible", with the CST saying it would "rely upon upon police advice regarding whether or not such trips should proceed."
The CST stressed that there was "no information suggesting a particular or imminent threat to the Jewish community", but said that "we have, nevertheless, seen attacks on Jews in France and Denmark occurring shortly after attacks upon others.
"We are, therefore, advising commercial security companies and security volunteers operating at all Jewish locations to ensure that they perform their duties as professionally and thoroughly as possible.
"In particular, we are asking that security personnel politely request people to avoid gathering in front of locations, such as parents outside schools, or congregants outside synagogues."
Shomrim, the volunteer security group, said police were advising community members to “remain extra vigilant” following the attack.
Additional police patrols were visible in Stamford Hill and other areas with large Jewish populations.
A number of Jewish political aides and staff have reported they are safe inside the Parliamentary estate.
Police said it was treating the incident as a terrorist attack. Eyewitnesses reported seeing a 4x4 car driving in a zig-zag along Westminster Bridge, hitting a number of pedestrians.
Pictures on social media networks showed the car hit a barrier outside Parliament, and a man reportedly ran into the Parliamentary estate and attacked a policeman.
A number of people are known to have died. MPs and staff remain on lockdown within Parliament.
Grant Shapps, Welwyn and Hatfield MP, tweeted his account of the incident.
“Walking through the Commons cloisters to vote, heard four gunshots. Police had MPs hit ground and crawl to cover,” he posted.
“Police response instant. Heard commotion, looked round. Police weapons drawn, four shots, police ordered us to hit ground and get back, get back.”
Responding to the incident, Chief Rabbi Ephraim Mirvis said: “Today’s attack, which targeted the very heart of our democracy in Westminster, will serve only to unite us against the scourge of violence and terrorism.
“The prayers of the Jewish community are with the families of the victims and with our security services, who so often selflessly place themselves in harm’s way for our protection."
A Board of Deputies spokesperson said: “The thoughts and prayers of everyone here go out to the victims, families and everyone caught up in today’s attack at Westminster.”
Stephen Pack, United Synagogue president, said the US was “horrified by the attacks that happened in London today and saddened by the rise in such incidents around the world.
“Our sympathies are with all those affected and we pray for the recovery of those wounded. We join with all other peace loving people to condemn such attacks.”
Micky Rosenfeld, Israel’s national police spokesman, said in the hours after the attack it was important for police and security services to heighten the alert.
He said police moves to lock down Parliament and keep MPs safe showed it was doing “exactly what you would want to happen following an attack like this.
“It is a correct move. The last thing London needs is MPs walking around the streets. The police priority needs to be to secure the area and make sure there is not a second attacker or any explosives.”
Earlier this month Mr Rosenfeld called on Britain to up its game in trying to combat terrorism, saying there should be an improved public awareness programme in the UK about potential threats.
Mr Rosenfeld said the police had responded correctly to the attack today by informing “Londoners quickly about where is safe to go and where is not".
Ronald Lauder, the president of the World Jewish Congress, condemned the attack as a "callous and calculated strike at the heart of Britain’s democracy".
He said it seemed "beyond coincidence that this attack was carried out on the first anniversary of the two terror attacks in Brussels, in which so many people were murdered. Terrorists around Europe and the world are trying to challenge our democracy and liberty. They will not succeed."
In Tel Aviv, the city hall was lit up in the colours of the Union flag in tribute.