A shooting in the northern West Bank on Friday killed two Israeli sisters and seriously injured their mother, adding to an already tense atmosphere in Israel and the occupied Palestinian territories during a holiday week marred by violence.

The sisters, 21 and 16, lived in Efrat, a settlement just south of Jerusalem, according to a statement from Oded Revivi, the mayor of Efrat. Their mother, who is in her 40s, was injured in the attack, Revivi said in a voice message. They were driving in a car in the Jordan Valley, while the rest of the family drove ahead in a separate car. The family, which has lived in Efrat for two decades, was on its way to a holiday gathering in the north when the attack occurred, Revivi said.

Police have not yet released the names of the victims.

Israeli medics said they pronounced the sisters dead at the scene. The older women was “suffering from severe multi-system injuries,” and they had airlifted her by helicopter to a hospital. A video shared by the Magen David Adom, Israel’s national emergency medical service, shows a white car that had driven off the road and appeared to have crashed into a tree. Two body bags could be seen several feet away.

Emergency services initially responded to the incident as a car accident, but Israeli soldiers who arrived at the scene found bullet holes in the Israeli car and assessed it had been attacked, the Israel Defense Forces said in a tweet.

Israeli soldiers blocked roads around the scene and were searching for the perpetrators of the shooting, which they are treating as a terrorist attack, the Israel Defense Forces said on Twitter Friday afternoon local time.

Hamas, the Palestinian militant group that controls the Gaza Strip, praised the shooting in a statement, though it did not explicitly claim responsibility.

“We congratulate the Jordan Valley operation and warn the occupation against continuing its aggression against our Palestinian people and the blessed Al-Aqsa Mosque,” the group said.

Defense Minister Yoav Gallant ordered an increased security presence across the country. Prime Minister Benjamin Netanyahu’s office said in a tweet he would hold a security assessment after the shooting. Police Commissioner Kobi Shabtai called on licensed Israelis to carry their firearms in the wake of the attack, Israeli newspaper Haaretz reported.

General Yehuda Fox, who commands troops in the West Bank, called the attack “extremely severe,” the Times of Israel reported.

“We’ll settle the score with these terrorists too, we’re hunting them and will catch them,” he said.

The shooting came after a night of violence, during which the Israeli military carried out airstrikes on Lebanon early Friday and continued attacks on the Gaza Strip in response to a barrage of rockets fired from south Lebanon toward northern Israel. The exchange of rocket fire followed two Israeli raids on al-Aqsa Mosque, on the sensitive religious site known to Jews as Temple Mount and to Muslims as the Noble Sanctuary. Police forced their way into the compound again around dawn Friday.

The Muslim holy month of Ramadan coincided with the Jewish Passover holiday this week, an overlap Israeli security officials have long warned could lead to further escalation.

Political instability in Israel and increased violence in the West Bank have added to the combustible situation. Israeli forces have killed at least 81 Palestinians in the West Bank so far this year, including 16 minors, according to the latest figures from the United Nations. Before the killings Friday, at least 14 Israelis had been killed by Palestinians in Israel and the occupied Palestinian territories this year.

“Horrified to see the deadly terror attack in the West Bank today, where a mother was critically injured, and her two daughters were killed,” U.S. Ambassador to Israel Tom Nides said on Twitter on Friday. “Praying for peace as we continue to observe the holidays.”

The European Union’s ambassador to Israel, Dimiter Tzantchev, also condemned the attack, saying, “Violence is never justified.”

Israeli opposition lawmakers expressed condolences to the victims and prayers for the injured woman.

Right-wing lawmakers in the governing coalition, meanwhile, called for a tougher response by the government in the Palestinian territories.

After the shooting, angry settlers blocked roads leading to Ramallah and to the Palestinian village of Huwara. The scenes resembled those from late February when, after two Israeli brothers were killed by a Palestinian gunman, settlers went on a retaliatory rampage through Huwara and surrounding communities, attacking Palestinians and setting fire to homes and businesses.

Louisa Loveluck, Jesse Mesner-Hage and Sufian Taha contributed to this report.