Anti-Semitic incidents are on the rise in Europe, but lack of proper data and "gross under-reporting" make it hard to document the trend, an EU institute has said.

The findings come in a report by the Fundamental Rights Agency (FRA) in Vienna, published on Wednesday (30 September).

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In France, the CNCDH, an official watchdog, recorded 851 incidents last year compared to 423 in 2013. It said 108 of them included physical violence, compared to 49 the year before.

German police noted 1,596 "crimes with an anti-Semitic motive" compared to 1,275 in 2013. The Amadeu Antonio Foundation, a German NGO, recorded 173 incidents compared to 65.

L’Osservatorio anti-semitismo, an Italian NGO, noted 86 incidents compared to 49.

The Polish interior ministry recorded 39 incidents compared to 25.

Spanish police recorded 24 compared to three in 2013.

The Community Security Trust, a UK charity, said there were 1,168 incidents last year compared to 535 the year before. Eighty of them were violent assaults, while the majority were "abusive behaviour".

Belgian, Czech, and Dutch authorities and NGOs also marked sharp increases. The trend was less marked, but still on the rise in Austria, Denmark, Finland, and Greece.

Hungary and Sweden were the only EU countries which noted a decreasing trend.

The other 13 member states either recorded zero incidents (Croatia, Cyprus, Latvia, Luxembourg, and Slovenia) or had no official or unofficial data.

But the FRA warned that the varying nature of the data available makes it impossible to compare levels of hate crime from EU state to state.

The "incidents" vary in gravity, from killings of Jewish people in Belgium, Denmark, and France by Islamist radicals, to desecration of Jewish graves by far-right groups in the Netherlands, or, more generally, posting of hate speech on the internet.

The FRA report noted that perpetrators often link Israeli state actions to local Jewish communities in Europe.

It said incidents "intensify in periods when conflict in the Middle East flares up".

It also said sporting events act as flashpoints, noting, for instance, "a torrent of anti-Semitic abuse" on the internet in Spain after a basketball game in Madrid with Maccabi Electra, an Israeli team.

Constantinos Manolopoulos, the FRA’s head, warned of a "climate of intolerance" in Europe and called for "immediate and decisive action to combat extremist, xenophobic, and anti-Semitic discourse and crimes".

The EU agency, also on Wednesday, published a separate report on Combating Intolerance and Hate, timed to coincide with a European Commission "colloquium" on the issue in Brussels the same day.

The report said there’s a "cacophony of racist and intolerant discourse" in Europe, which "influences mainstream politics at national, and more importantly at local level".

It cited a 2008 survey - the latest one available - of 23,500 migrants and minorities in the EU.

The survey showed that 37 percent of migrants had experienced "discrimination", but 80 percent didn't report incidents to police.

Roma people (50%) reported the most abuse, followed by sub-Saharan Africans (41%), and north-Africans (36%).