Poland’s prime minister on Wednesday condemned what he described as a “xenophobic act of aggression” on the country’s ambassador to Israel, who was spat at and verbally abused on a Tel Aviv street at a time of rising tensions between the two nations.

Israeli officials expressed shock at the assault on Marek Magierowski on Tuesday afternoon and were investigating the incident. Israeli police said they had detained and released a 65-year-old man suspected of approaching the ambassador, who was sitting in his car in front of the Polish Embassy, and spitting at him.

Police spokesperson Micky Rosenfeld said the suspect remained under house arrest until Thursday and is “not permitted to be in the area of the Polish Embassy for 30 days.”

The incident comes amid a bitter standoff between Poland and Israel over how to remember the Holocaust and over demands that Poland pay reparations for former Jewish properties that were seized by Nazi Germany during the Second World War and later nationalized by Poland’s communist regime.

Israeli Ambassador Anna Azari was summoned to the Polish Foreign Ministry in Warsaw on Wednesday over the incident. Michal Dworczyk, the head of Polish Prime Minister Mateusz Morawiecki’s office, said the Polish government expects the perpetrator to be punished.

Morawiecki expressed his concern at what he described as a “racist” attack.

“Poland strongly condemns this xenophobic act of aggression. Violence against diplomats or any other citizens should never be tolerated,” Morawiecki said.

The New York-based American Jewish Committee said it was “stunned” by the attack.

“Violence against a diplomat is totally unacceptable,” chief executive David Harris said, calling the attack “outrageous.”

Israel expresses ‘full sympathy’

Harris stressed the role of dialogue as a way of addressing any disagreements and reinforcing the “longstanding, strong, and mutually beneficial Israel-Poland relationship.”

The U.S. ambassador to Poland, Georgette Mosbacher, tweeted her support for Magierowski, condemned the attack and expressed an expectation that the assailant would be brought to justice.

Israeli Foreign Ministry spokesperson, Emmanuel Nahshon, said the assault was being investigated and that “we will update our Polish friends” on what is found.

“Israel expresses its full sympathy with the Polish ambassador and shock at the attack,” Nahshon said. “This is a top priority to us, as we are fully committed to diplomats’ safety and security.”

Ties between the two countries became strained in January 2018 when Poland passed a law that criminalized blaming the Polish nation for the crimes of Nazi Germany during the Second World War. Poland’s conservative nationalist government described it as an effort to end linguistic formulations, such as “Polish death camps,” to refer to the death camps that Germans operated on occupied Polish territory during the war.

However, many people in Israel felt it was an attempt by the Polish government to repress debate and scholarship looking at the cases of those Poles who helped the Nazis in killing Jews during the occupation, and even after the war ended.

The law was softened but bad feelings have continued to simmer, with tensions coming to the surface from time to time.

Earlier this week, the Polish government canceled a visit by an Israeli delegation, saying the Israeli government made last-minute changes that suggested it would focus on the issue of the restitution of former Jewish property. The Polish government insists that the matter is closed and that because it lost so much in the war it will pay nothing.