Prime Minister Rami Hamdallah said upon his return to Ramallah on Tuesday coming from the Gaza Strip where he escaped an assassination attempt that the attack against his convoy was well prepared and the bomb was buried two meters into the ground.
Palestinian intelligence chief Majid Faraj was part of the convoy, the source said.
According to the Jeddah-based OIC, the reported attack sought to disrupt "Palestinian national unity and the [inter-Palestinian] reconciliation process".
Another senior official, Tawfiq Abu Naim, said "whoever who did this only serves the [Israeli] occupation and is doing what the occupation demands".
The assassination attempt, he added, was in "concordance" with all attempts to stop the PA government from assuming its responsibilities in the Gaza Strip.
The office of President Mahmoud Abbas said it "holds Hamas responsible" for the "cowardly attack", and Hussein al-Sheikh, a member of Fatah's Central Committee who is the authority's minister of civil affairs, called Hamas "fully responsible". One auto door also appears to have blood on it.
He travelled overland, via Israel, to the Gaza Strip, and police said the motorcade was attacked near the enclave's northern town of Beit Hanoun.
The Palestinian Authority said it held Hamas responsible for the attack, but stopped short of directly accusing the group of carrying out the assault, suggesting it had failed to provide adequate security.
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The Hamas party won Palestinian legislative elections in January 2006, then consolidated power the following year after factional fighting between Hamas and forces loyal to the Fatah party. Hamas has accused Fatah of neglecting Gaza and inflicting misery on inhabitants through sanctions.
Hamdallah was in the area to give a speech at the opening of a sewage plant, which he did only a few minutes after the attack.
Gaza, which is separated from the West Bank by Israeli territory, has been controlled Hamas since the militant group ousted the PA in 2007.
Greenblatt - who alongside Jared Kushner was tasked by Trump with finding a way to resume stalled Israeli-Palestinian peace talks - said "we regret" that the Palestinian Authority boycotted the meeting.
The Hamas interior ministry confirmed there had been an explosion and said security forces were investigating the incident.
He commended Hamdallah's "leadership and continuing efforts to address the dire humanitarian situation in Gaza and achieve reconciliation".
The World Bank, European Union and other European governments have provided almost $75 million in funding for the project.