There is a feeling of "anxiety" among Jewish communities in the UK following the shootings in Paris in which people were killed in a Kosher supermarket and a Jewish security charity said it has received an "unusually high" number of calls.

As people mark Holocaust Memorial Day on Tuesday - also the 70th anniversary of the liberation of Auschwitz-Birkenau where more than a million prisoners were killed - not a month will have passed since the terrorist attack in the Jewish supermarket killed four people.

Mark Gardner, a spokesman at Community Security Trust (CST), said the number of calls they are receiving from Jewish people fearing a Paris-style terrorist attack in the UK is "unusually high".

Last week he said the number of calls they had received had been "unprecedented", and it has only "diminished slightly" since.

"I think fears continue to be really unusually high," he said.

Mr Gardner said people's fear lies in an understanding of the "reality of terrorism".

Four hostages were killed by Amedy Coulibaly at a Jewish supermarket earlier this month in attacks timed to follow the massacre of 12 people by brothers Said and Cherif Kouachi at the offices of satirical magazine Charlie Hebdo.

Scotland Yard assistant commissioner Mark Rowley, the national policing lead for counter-terrorism, said last week there was a ''heightened concern'' about the risk to the Jewish population in the UK since the attacks and a security review would be carried out.

Mr Gardner said there have been terrorist attacks against Jewish communities for many years and referred to the "phenomenon that's repeated many times" when there is a conflict situation in the Middle East and then there is a "significant increase in the number of anti-Semitic race hate" incidents.

"Every time one of these conflicts occurs, unfortunately there's an increase in anti-Semitic incident levels. And people get very concerned by that," he said.

Meanwhile, Karen Pollock, chief executive of the Holocaust Educational Trust, said that while there are feelings of "anxiety" and "vulnerability" in the Jewish community, she also said the threat of anti-Semitism is not new in recent times.

"In light of events in Paris, it is true that there is more anxiety and possibly a feeling of vulnerability, felt more acutely in the Jewish community. I think for Holocaust survivors particularly, you can understand that," she said.

Adding: "The fact is that the threat of anti-Semitism is one that is not new. It is not something that we only, as a community or as a country, started to be aware of after Paris. Even over the summer when there was various protests and things written...on Twitter there was a hashtag saying Hitler was right.

"This isn't something that suddenly come to light. I think it's more that the attention has been drawn to it since the really horrific attacks on people in the Kosher supermarket in Paris, simply because they were Jews," she said.

Ms Pollock referred to the defacing of posters advertising a Holocaust Memorial Day event in Newham, east London, last week.

"The scary thing about that is that somebody would feel...that somebody would go out of their way to do that. But then the positive thing is the amount of rejection from society of that act, whether on Twitter, but also in emails we received, and people commenting elsewhere, saying this does not reflect our society and it's not how we feel.

"I think it's up to all of us as a country, not just the Jewish community, just to be vigilant, and also to recognise - something we always talk about at the Holocaust Educational Trust - it's about language, it's about behaviour, and noticing those warning signs and not letting things get out of control," she said.

Holocaust survivor Ivor Perl, 82, who lives in Essex, said he is afraid.

Asked about how he felt, he said: "Truthfully? Yes of course I feel fearful. How can I not be? I mean, if a child burns his finger in a fire, won't he be always scared of a fire? How can I not be frightened?"

But fellow Auschwitz survivor Freddie Knoller, 93, who lives in north London, said his optimism prevails.

"It is terribly, terribly worrying for us survivors and also probably for the Jewish community. But I only hope, that's my optimism, I only hope that this will not...that the things that happened before will not happen again.

"I'm not afraid, no. I'm not afraid. It's because of my attitude. Maybe some people are...my wife is not as easy going as I am," he said.

Holocaust survivor Eve Kugler, 84, who also lives in north London, said she thinks a Paris-style terrorist attack could "probably" happen in the UK.

She said she has got used to the tight security at Jewish services she attends, and described the security at Holocaust Memorial Day as "intense".

"The security is very, very intense at Jewish events," she said, adding that she was unsure whether there would be any more security this year than last year.

"You have a gathering of a few thousand people, Jewish people mostly, commemorating the Holocaust...you have to have security. I didn't like it. Now I just shrug my shoulders and accept it as a way of life. I accept it now. I used to think it was absolutely awful, what kind of a country is this?," she said.

The Holocaust Educational Trust aims to educate young people from every background about the Holocaust and the lessons to be learned for today's world.