Three people who allegedly threw firebombs at a synagogue in Gothenburg have been arrested as Jewish groups condemned the attack and demanded authorities take action.

The attack, the second such anti-Jewish incident in Sweden in two days, occurred during a youth event at the synagogue and the adjacent Jewish centre in the country’s second-largest city.

Witness Allan Stutzinsky said he saw a dozen masked youths throwing what appeared to be firebombs into the garden surrounding the synagogue but they failed to damage the building.

No-one was injured in the incident on Saturday night, which is being investigated as attempted arson.

It happened after some 200 people rallied late on Friday in the city of Malmo, shouting anti-Jewish slogans and waving Palestinian flags to protest against US president Donald Trump’s decision to recognise Jerusalem as Israel’s capital.

“Highly morally objectionable 2 suggest that people want 2 murder a particular group because of a diplomatic statement& no one would dare 2 suggest that any other group could justifiably be targeted because of what happens with a nation they are seen to be connected 2” Dr Kantor https://t.co/IZLPRKbFRg — European Jewish Congress (@eurojewcong) December 10, 2017

The incidents were condemned by Swedish prime minister Stefan Lofven and other top politicians, and authorities increased security around the synagogue and at Jewish centres in Stockholm and Malmo.

The European Jewish Congress said it was “unconscionable that Jews are under attack on the streets of Europe” and urged Swedish and other European governments to take “strong punitive action” against perpetrators.

Mr Lofven said: “I’m terribly upset over the attack on a synagogue in Gothenburg yesterday and calls for violence against Jews at a demonstration in Malmo.”

“There is no place for anti-Semitism in our Swedish society. The perpetrators will be held accountable.”

He urged “all democratic forces” in Sweden to work together to create “a tolerant and open society where everyone feels safe”.

The attack is the second such anti-Jewish incident in Sweden in two days (Adam Ihse/TT News Agency via AP/PA)

In neighbouring Finland, it was reported police would raise security measures around the Helsinki synagogue.

Meanwhile, the American Jewish Committee condemned a protest on Friday in Berlin, during which American and Israeli flags were burned in front of the US embassy.

Deirdre Berger, director of the committee’s Ramer Institute in Berlin, urged an “unequivocal response” from German politicians, saying “the protests have to be condemned”.

Berlin police said 10 people were detained and 12 criminal complaints were filed over the protest against Mr Trump’s decision to move the US embassy from Tel Aviv to Jerusalem.