Palestinian Prime Minister Rami Hamdallah has escaped unharmed after an explosion targeted his convoy in Gaza.
No group has said it carried out the attack, which injured several guards.
The Palestinian Authority said it was an assassination attempt and that it held the militant Hamas movement, which dominates Gaza, responsible.
Hamas said the attack was an attempt to damage Gaza's security and "deal a blow to efforts to finalise reconciliation" between the main Palestinian factions.
Palestinians in Gaza and the West Bank have been ruled separately since a rift between Hamas and President Mahmoud Abbas's Fatah faction erupted in violence in 2007.
Hamas won parliamentary elections in the occupied territories the previous year, and reinforced its power in Gaza after ousting Fatah from the enclave.
Last October, the rivals signed a reconciliation deal that was meant to see Hamas hand over administrative control of Gaza to the Fatah-dominated Palestinian Authority. But disputes have delayed the deal's full implementation.
A Palestinian security official said Mr Hamdallah and the head of intelligence, Majed Faraj, appeared to have been targeted by a roadside bomb.
The explosion damaged three cars in their convoy, which had just entered Gaza through the Erez Crossing with Israel.
Several security guards were hurt by the blast, which left a crater in the tarmac.
Shortly afterwards, Mr Hamdallah spoke at the opening of a wastewater treatment plant in Gaza and pledged to continue reconciliation efforts.
"The explosion will not stop us from completing the national reconciliation and will not stop us from coming to Gaza," he said in a televised speech.
Mr Hamdallah later returned to the West Bank.
President Abbas called the attack "a desperate attempt that serves the interest of those who want at this critical period to liquidate the Palestinian cause and to deny the Palestinian people their right to achieve freedom and independence".
Mr Faraj said: "It is too early to accuse anyone, but those who are in charge shoulder the full responsibility for security on the ground."
Hamas condemned what it called an "ugly crime" and said it had launched an investigation.
Spokesman Fawzi Barhoum said it believed the attack was carried out by the same people who last year assassinated Mazen Fuqaha, a commander of Hamas' military wing, and attempted to assassinate Maj Gen Tawfiq Abu Naim, the head of Gaza's internal security forces.
The UN Special Co-ordinator for the Middle East Peace Process, Nickolay Mladenov, also condemned the attack, saying it had to be promptly investigated and the perpetrators brought to justice.
"Until the legitimate Palestinian Authority is fully empowered in Gaza, Hamas has the responsibility to ensure that the government is able to carry out its work in the strip without fear of intimidation, harassment and violence," he added.