If the din generated by protesters supporting the Palestinian Arabs that took place Wednesday evening at Athens was any indication, it may well be a noisy week. Riot police had to intervene and fire tear gas to disperse a march of  an estimated 10,000 persons who tried to advance on the Israeli embassy.

Some 260 miles to the east, something more sinister happened when Palestinian and Syrian migrants protesting Israel attempted to break out a refugee holding facility on the Greek island of Samos. Greece, like Italy, is on the frontlines of Europe’s worsening migrant crisis. There are about 3,000 Palestinians in detention centers throughout Greece, while the Samos detention center houses 4,000 detainees, of which about a fifth are Palestinian.

According to a report in the Greek newspaper Protothema, the detainees have been receiving messages of incitement against Israel “from Hamas” on various smartphone apps. With Hamas now more on the backfoot than in previous days, owing largely to Israeli’s counterattacks in the Gaza Strip following the terrorists’ group deadly attacks in southern Israel on October 7, this raises the question: Is Tehran, Hamas’s leading backer, using technical and other means to stoke the rise of anti-Israeli protests around Europe?

That possibility, which has potentially major security implications for Europe as well as America, cannot be ruled out. What is certain is that the refugees in Samos intended to cause a disturbance Tuesday night when a group of around 700 began shouting statements in favor of the Palestininans and Hamas and tried to bust the compound’s doors. Greek police arrested seven people, five of whom were charged with inciting violence. 

At Athens on Wednesday the protest appeared to be closely monitored by police and after an hour had largely dissipated. But in the interval between an explosion at a hospital in Gaza on Tuesday night and President Biden’s confirmation on Wednesday that the Palestinian Islamic Jihad terrorist group was responsible for it, tensions around Europe mainly worsened. 

They did so even as governments’ response to the war in Israel differed. Last week the French foreign minister ordered that “pro-Palestinian protests, because they are likely to generate disturbances to public order, must be banned.” In France — where tout le monde has an opinion — the highest court weighed in on Wednesday, stating that such protests must be banned on a case-by-case basis. 

Anti-Israel protests and incidents of antisemitism have rippled across Europe, notably in Germany and Britain. On Wednesday night assailants firebombed a Berlin synagogue with two Molotov cocktails. The extent of the damage was not immediately clear. 

There were also reports of assaults by pro-Palestinian demonstrators Wednesday on a synagogue in the Spanish North African enclave of Melilla, and on an another synagogue in Tunisia, in which significant damage was reported.  

In the Greek city of Thessaloniki on Wednesday, police were alerted to a black suitcase deposited outside the city’s Jewish Museum. Police cordoned off the area and after they inspected the suitcase found nothing inside, but the incident nevertheless put residents on edge. The northern city was once home to Greece’s largest Jewish population, decimated in the Holocaust. 

Prime Minister Mitsotakis, who counts himself as a good friend of Prime Minister Netanyahu, has concerns of his own, including about the possibility of regional escalation. In an interview with Greek television on Wednesday night, he said, “I’m concerned about the possibility of a ground invasion of Gaza,  Hamas may want to provoke it.”

Mr. Mitsotakis also singled out Turkey for its less than robust support for Israel as the battles against terrorist targets in Gaza continued into the week. He said the Turks have displayed a problematic attitude by not condemning Hamas, especially given that the only recognized Palestinian administrative entity is that of Fatah. “The terrorist attack was brutal, we have never seen anything like it before,” Mr. Mitsotakis also told Greek viewers, adding, “We defend Israel’s right to self-defense. We are an ally of Israel.”

The premier also addressed the incident at the island refugee center, saying he was not overly concerned but that “the authorities are watching,” adding, “We did not have in Greece characteristics of Muslim populations that became radicalized, but we are careful.”

Radicalized Muslim communities are, though, a problem elsewhere on the Continent, as demonstrated by the  terrorist attack in Belgium this week. In that attack, a gunman who claimed to be inspired by the Islamic State shot and killed two Swedish nationals. Belgian officials suggested but would not confirm that the terror attack was linked to the Israel-Hamas war.

Also on Wednesday, seven airports in France plus the Palace of Versailles were evacuated following “threats of attack,” a police source told the Agence France-Presse. Prior to that mayhem, on Saturday — one week after the Hamas onslaught in southern Israel — the Louvre was evacuated because of a bomb threat. 

Throughout Europe there appears to be a growing disconnect between  the support for Israel expressed by some leaders and the discontent on the streets. Following his quick trip to Israel, Chancellor Scholz stated on X, “Brutal terror. The execution of defenseless civilians. Murdered infants, abducted children. Humiliated Holocaust survivors. It makes our blood run cold.”

On the other end of the spectrum, there are several European politicians whose criticism of Israel and defense of Palestinians flirts with what a Boston University professor of history once described to this correspondent as a sort of “genteel antisemitism.”

 In France, say, left-wing parliamentarian Daniele Obono of the France Unbowed party praised Hamas as a “resistance” movement. That drew a swift rebuke from the interior minister, Gerald Darmanin, who said on Tuesday that Ms. Obono should face a criminal investigation for apparently trying to justify terrorism. 

The demonstration at Athens Wednesday was organized in part by left-wing groups. One prominent Greek politician, a Marxist-leaning former finance minister, Yanis Varoufakis, has accused Israel of committing “war crimes” in Gaza and accused the Israeli government of having “apartheid policies.”

Reflexive anti-Israeli invective from the left is par for the course in Europe. It is the facile attempts at moral relativism by the EU’s foreign policy chief, Josep Borrell, that encapsulate many Europeans’ missteps here. “We cannot make the people of Gaza responsible for the terrible actions of Hamas,” Mr. Borrell stated. Is that so?