The truck smashed into the Armon Hanatziv promenade in the Israeli capital, Jerusalem, this morning.
ZAKA, a voluntary emergency response team, said sources on the ground had confirmed four people's deaths.
It added that there were 15 victims, several of them in serious condition, and that the perpetrator had been killed.
Benjamin Netanyahu, Prime Minister of Israel, said the driver - a Palestinian - was likely an ISIS supporter.
Various sources are also reporting that the suspect's father and brother were arrested in the aftermath of the attack.
Israeli newspaper Haaretz said there were people stuck underneath the truck, and that three women and a man were dead.
The Times of Israel said one seriously-injured female victim was sent unconscious, in an unstable condition, to Shaare Zedek hospital.
Of the others sent to Shaare Zedek, four were lightly injured and one was in a moderate condition, MDA said.
Seven more victims were sent to Hadassah Hospital Ein Kerem - three in a moderate condition and four were lightly wounded.
The Times of Israel said the police are treating the incident as a potential terror attack, though the cops claim an investigation is ongoing.
Initially a second terror attack was feared in the southern neighbourhood of Har Homa, but the claim was ruled out by the authorities.
(Click here for Android APP of IBTN. You can follow us on facebook and Twitter)
About sharing
After Pakistan, India issues instructions for Indian students living in Kyrgyzstan<...
Iraqi army claims major explosion at a base south of Baghdad
Sat...
What did Iranian media say about Israel's attack?
Friday, Ap...
What did the US Secretary of State say about Israel's attack on Iran?<...
Australia instructs its citizens to leave Israel amid Iran-Israel tension<...