(Reuters) — Two women and a man were killed and one person seriously injured in a likely “terrorist” shooting in central Brussels at the city’s Jewish Museum on Saturday, officials said.

An Israeli couple was among the victims, Israeli sources told Haaretz. A third victim was a museum volunteer. The fourth was a museum worker who died early Sunday.

The city’s mayor said on Twitter that the killings took place inside the museum and that the attacker fled in a car. A suspect was later arrested but later freed after officials said he was not involved. A government officials said the attack was being treated as a likely anti-Semitic incident.

A spokeswoman for Brussels prosecutors office said there was no clear information about the perpetrator, although a fire brigade official said earlier that the shooter had driven up to the museum, gone inside and fired shots.

“Regarding the motive, we have little information. Everything is possible,” Ine Van Wymersch told a news conference.

“We know that the location, the Jewish Museum in Brussels, makes one think of it being an anti-Semitic attack, but we do not have enough to confirm this is the case.”

Belgium’s interior minister, Joëlle Milquet, was quoted by the RTBF Belgian television station, saying: “It’s a shooting … at the Jewish Museum … All of this can lead to suspicions of an act of anti-Semitism.”

Brussels Mayor Yvan Mayeur told the BBC that the shooting was probably a “terrorist act”.

“It’s clearly extremely serious,” he was quoted as saying, “and on the Jewish Museum too, which isn’t a coincidence”.

Police cordoned off the area around the museum in central Brussels, a busy tourist district packed with cafes, restaurants and antique furniture shops. An annual outdoor jazz concert due to be held in a popular square near the museum was called off.

A man seen by witnesses driving away from the scene was questioned in connection with the shooting, but officials were not certain if there had been one or more perpetrators, or whether the man had been involved.

“The link between this person and the incident is not clear. The person does admit being present,” Van Wymersch said.

Security around all Jewish institutions in the country has been raised to the highest level, and Prime Minister Elio Di Rupo met with police and senior officials to discuss the situation.

About half of Belgium’s 42,000-strong Jewish community lives in Brussels.

Jewish community officials drew parallels between the shooting and the 2012 killing of four Jews in a school in France by an al Qaeda-inspired gunman, Mohamed Merah.

“This really reminds of what you experienced in France with Mr. Merah attacking a Jewish school,” Maurice Sosnowski, president of the Coordinating Committee of Belgian Jewish Organizations, was quoted saying by BFM TV.

“This is appalling. I would never have imagined something like that happening in Brussels.”

He said no threats have been issued to the Jewish community.

World Jewish Congress President Ronald S. Lauder urged Belgian authorities to protect Jewish sites in the country.

“Two years after Toulouse…this despicable attack is yet another terrible reminder of the kind of threats Europe’s Jews are currently facing.”

Henry Goodman, president of the Jewish Community Center in Brussels, told CNN he was “horrified” by the attack.

“We didn’t expect such a terrible act. Since we don’t know who has done it or the reason, we can only imagine that it is an act of pure anti-Semitism,” he told the network.

“While we don’t not yet have full information regarding the background to this attack, we are acutely aware of the permanent threat to Jewish targets in Belgium and across the whole of Europe,” European Jewish Congress President Moshe Kantor said in a statement.

Belgian Jewish community leader Joel Rubinfeld told the Guardian that the attack was clearly ” a terrorist act” and the result of “a climate of hate.”

At the time of the shooting, pro-Palestinian groups were holding a concert and political rally in another part of Brussels.

Pierre Galand, a leader of the Belgian-Palestine Association, interrupted speeches denouncing Israel and its occupation of Palestinian territory to request a minute of silence for the victims of the shooting, the New York Times reported.

“This is an extremely odious crime,” Mr. Galand told the crowd, the paper reported, adding that it is “primitive anti-Semitism.”

On Sunday, Belgium holds a general election and throughout Europe, voters will choose the next European Parliament.”

Like elsewehere in Europe, anti-Semitic far right wing groups have been on the rise in recent years.

A right wing lawmaker recently held a Brussels summit meeting for anti-Semites from across the continent. Police banned the gathering and clashed with protesters at a related demonstration.