Jerusalem explosion: Israeli rescue services report 21 casualties after blast on bus

Police commissioner says there is 'no doubt' it was a terror attack

Images on social media showed smoke billowing from the burned-out bus (Micky Rosenfeld/Twitter)

At least 21 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.

Emergency workers search the scene after a blast on a bus in Jerusalem (Reuters)

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.

Israeli security officials search the remains of a burnt out bus following an explosion in Jerusalem (AP)

The Magen David Adom rescue service said 21 people had been wounded, including two seriously.

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.

Around 189 Palestinians, 28 Israelis and two American citizens have been killed since the latest wave of violence broke out in October.

Additional reporting by agencies