At least 16 people have been injured after a bomb exploded on a bus in Jerusalem.
"There is no doubt that this was a terror attack," Jerusalem police commissioner Yoram Halevy said.
He added that it was too early to know who was responsible or whether it was a suicide attack.
"We are investigating where the explosive device came from, who planted it, how it got on the bus. All this is in the initial stages of investigation," he said.
Local media reported that one man who was injured was under investigation. It is thought he was not carrying any identification papers.
Images on social media showed smoke billowing from the burnt out bus on Hebron Road, in the south-west of the city.
The Magen David Adom rescue service said 16 people had been wounded, including two seriously.
Bom afgegaan Hebron Road Jerusalem pic.twitter.com/WiS1OL39wF— Sieb Buiten (@SiebBuiten) April 18, 2016
Huge bus explosion in Jerusalem, possible terror attack. Many emergency forces on-scene. pic.twitter.com/rPlFI0tPLr— Israel Breaking (@IsraelBreaking) April 18, 2016
Attacks on Israeli buses by suicide bombers were a hallmark of the Palestinian uprising in 2000-2005 but have been rare since.
Tensions have been brewing over a series of skirmishes between Israeli forces and Palestinian militants.
Israeli security officials search the remains of a burnt out bus following an explosion in Jerusalem (AP)
Almost 200 Palestinians, 28 Israelis and two American citizens have been killed since the latest wave of violence broke out in October.
At least 189 Palestinians have been killed in that period. Israel says most of the dead were attackers, with the rest killed in clashes.