BETHLEHEM (Ma’an) -- An explosive device detonated on an Israeli bus Monday evening in southern Jerusalem, injuring 21, Israeli police said.
Israeli police spokeswoman Luba al-Samri said the explosion took place in the back of a No. 12 bus while it was holding passengers, before causing fire to a nearby bus and private vehicle.
The explosion -- deemed by the Israeli authorities as an attack -- was not immediately claimed and Israeli police said investigations had been launched into the source of the bomb.
A spokesperson for Hadassah Hospital told Ma'an seven of the injured were being treated at its Ein Karem branch, with four in moderate to severe condition and three in light condition. Three others were being treated at Hadassah's Mount Scopus hospital, all in light condition.
A spokesperson for Shaare Zedek Hospital told Ma'an eight were being treated at the hospital, including one in severe condition who was undergoing an operation. She said the seven others were in "very light" condition.
Jerusalem Mayor Nir Barak quickly condemned the explosion as a "terror attack," and Israeli Prime Minister Benjamin Netanyahu vowed to "punish the terrorists" behind the incident.
"Israel will put its hand on whoever prepared the bomb and sent the terrorists," the PM's spokesperson said.
Knesset member and head of the Arab Joint List Ayman Odeh also denounced the attack.
"Civilian casualties are unacceptable and harmful to the struggle against the occupation," Odeh, a Palestinian citizen of Israel, wrote on social media. "Netanyahu's government is fueling the cycle of bloodshed. Only a political settlement will bring security to both (Israeli and Palestinian) people."
While not claiming responsibility for the explosion, several Palestinian groups hailed the reported attack.
"We bless the Jerusalem operation, and consider it a natural reaction to the Israeli crimes, especially field executions and the desecration of the Al-Aqsa Mosque," the Hamas movement said in a message on social media.
Meanwhile, Islamic Jihad said the explosion was a "strong message" that the Palestinian uprising was ongoing and alive, and that resistance was entrenched in Palestinian hearts and minds.
Popular Resistance Movement leader Haitham al-Ashqar said that "heroic operations" were "a natural and rightful response" to continuous Israeli violations against Palestinians.
Al-Ashqar called on Palestinian resistance fighters and "Intifada youths" to carry out more "heroic operations that hurt the occupation and its settlers."
More than 200 Palestinians have been killed by Israeli forces and settlers since a wave of unrest spread across the occupied Palestinian territory in October. The unrest has been marked by a surge of small-scale attacks carried out by Palestinian individuals -- predominantly on Israeli military targets -- which have left nearly 30 Israelis dead, with the majority of suspected Palestinian attackers shot dead on site.
Tuesday's alleged attack marked the first time an Israeli bus was targeted since 2005.