At least 16 injured in Jerusalem bus explosion (PHOTOS, VIDEO)

A bus has exploded in Jerusalem, leaving around 16 casualties, Israeli media report, citing emergency medical services.

The massive explosion occurred in Hebron Way, west Jerusalem, with police citing "a militant attack" as the probable cause of the blast.

Multiple social media posts show smoke coming out of the burned-out bus, which is standing in the middle of the road.

Initial reports indicated there were 20 casualties. Now Jerusalem Post reports 16 people were injured in the blast, with two injured "seriously," one "moderately," and five "lightly." The newspapers cite sources in the Magen David Adom emergency service.

Some of the injured were evacuated to Jerusalem's Shaare Zedek Medical Center. Others were taken to Hadassah Hospital nearby.

The bus was reportedly not carrying any passengers when it exploded, an Israel Police spokesperson said, as cited in the media. The casualties were apparently due to being close to the blast.

When I arrived at the scene I saw two buses going up in flames and about 10 causalities among them, one who was mortally wounded and another in serious condition,” Mickey Cohen, head of the Jerusalem emergency response service, told Haaretz.

Jerusalem district police say the bus could have been blown up by an explosive device or targeted by a suicide bomber who detonated the device inside the bus, according to news outlet Arutz Sheva.

Eugenia Ugrinovich, a freelance journalist in Jerusalem, has told RT that the police confirmed "there was an explosive device at the back of the bus that caused [the] fire," saying the casualties were suffering from injuries typical for an explosion.

She added that Jerusalem will be on high alert with security tightened in public places for days to come. The bus blast was the first since 2012, Ugrinovich said, adding that lone-wolf attacks like this are very difficult to prevent and will surely happen again in future.

According to the police, the bus departed from the southern part of the city and arrived at Moshe Baram Street, when apparently an explosion was heard and the bus caught fire.

Suicide attacks on Israeli buses took place regularly in the early 2000s, and became a hallmark of the Palestinian uprising. In March 2002, a suicide bomber blew himself up inside a bus in Jerusalem, leaving 25 injured. Several months later, another suicide bomb attack on a bus in northern Israel killed 17 and injured 43, most of them IDF soldiers.

Violence between Israelis and Palestinians has abated somewhat recently after a series of stabbing attacks last year. At least 21 Israelis and 131 Palestinians were killed in that spike of violence. 

READ MORE: Israeli army sweeps West Bank after ‘Palestinian terrorist’ stabs mother of six at settlement

In early January, at least two people were killed and several others injured following a shooting at a bar in central Tel Aviv. The gunman was described by an eyewitness as being "light-skinned and not Eastern looking," and as carrying an M-16. Further reports said the shooter, identified as 29-year-old Nashad Milkham, reportedly stole the gun from his father, who worked in the security industry.

The blast aboard the bus was caused by a bomb, Brachie Sprung, a spokeswoman for Jerusalem mayor Nir Barkat, told Reuters: "It was small, but it was definitely a bomb."

Police say the bus explosion was a terror attack after bomb disposal experts found parts of an explosive device at the scene.

Ruslan Kandaurov, head of the Russian Embassy’s consular section, has told TASS that one of the people injured in the blast is an Israeli-Russian dual national, who is presently “in moderate condition.”

Jonathan Hessen, a political analyst in Israel, told RT that Hamas has already claimed responsibility for the attack, carried out in response "for the atrocities, as they put it, committed by the State of Israel towards Al-Aqsa mosque and the Temple Mount." He said that Israeli leadership is committed to retaliate against any threat to citizens, but added that it will not necessarily escalate tensions between Israelis and Palestinians.