An 18-month-old Palestinian baby has died after suspected Jewish extremists set fire to his home in the occupied West Bank.
Israeli prime minister Benjamin Netanyahu condemned the incident and called it a "terror attack."
Several other family members were also injured in the blaze, military officials said.
According to the military, the suspects entered the village of Duma, near the city of Nablus, where they set the homes ablaze and scrawled graffiti, including "Long live the Messiah," "revenge" and "price tag."
The attackers threw Molotov cocktails, or fire bombs, at the houses, the military said.
The slain child was identified as one-and-a-half year old Ali Dawabsheh. His four-year-old brother and parents were among the wounded, according to Gassan Daghlas, a Palestinian official from the Nablus area.
Daghlas said Jewish settlers broke the window of a house and flung a fire bomb inside, "causing a quick and huge fire."
He added that three people were wounded aside from the child. The Israeli military said three people were critically wounded and one was slightly injured. The critically wounded were taken to Israeli hospitals for treatment, the military said.
The interior walls of the home were blackened as Israeli police surveyed the scene later on Friday morning. A brown couch was covered in white ash as charred debris lay strewn around the property.
"Setters in the Nablus area are very aggressive. They never stop attacking Palestinians in their villages and the Israeli government needs to put an end to these aggressions," Daghlas said.
The Israeli military said it sent troop reinforcements to the West Bank, fearing the incident could trigger unrest.
Jewish extremists have for years attacked Palestinian property, as well as mosques, churches and even Israeli military bases in opposition to what they see as the Israeli government's favorable policies toward the Palestinians, although it is rare for anyone to be killed in such attacks.
Friday's incident comes after Israel this week demolished homes in a West Bank settlement built without prior authorization. Israel shortly after announced plans for new settler homes in the same settlement and elsewhere.
Critics say police have been slow to apprehend the Jewish assailants and Palestinians say the military has failed to protect them from attacks by militant Jewish settlers in the West Bank.
The attacks, known as "price tag," have been condemned across the Israeli political spectrum and condemnations came swiftly Friday, with Prime Minister Netanyahu issuing a stern statement against the violence.
"I am shocked over this reprehensible and horrific act. This is an act of terrorism in every respect. The State of Israel takes a strong line against terrorism regardless of who the perpetrators are," he said.
Israeli military spokesman Lt. Col. Peter Lerner called the incident "nothing short of a barbaric act of terrorism."
Israeli Defence Minister Moshe Yaalon said Israel would not allow "Jewish terrorists" to carry out such acts.
"We will not allow Jewish terrorists to harm the lives of Palestinians in Judea and Samaria," he said in a statement, referring to the West Bank by its biblical name. "We will fight against them firmly and with all means and tools at our disposal."
Meanwhile, Israeli police said they would restrict entrance to Friday prayers at a Jerusalem mosque, permitting only male worshippers over the age of 50. There were no restrictions on women. Police said the decision was not necessarily related to the West Bank incident and comes as police received word that Palestinian youth at the mosque planned to cause disturbances.