People rush to help the injured
A roadside bomb in Lebanon has killed a senior Palestinian official and three others, said to be bodyguards, close to Mieh Mieh refugee camp near Sidon.
The bomb killed Kamal Medhat, deputy head of the PLO in Lebanon, but may have been aimed at the PLO's leader in the country, Abbas Zaki, sources said.
The blast blew one car off the road and badly damaged another, scattering burning debris.
There is no immediate indication of who may have been behind the attack.
Kamal Medhat recently attended a memorial for dead Hezbollah fighters
Condemning it, Fahmi Zaarir, an official in Mr Medhat's Fatah faction, said: "We do not accuse anyone at this point but we confirm that it was a targeted assassination."
Lebanon's crowded and poorly developed camps, housing Palestinians who were expelled from or fled what became Israel in 1948, are prone to violent unrest and insecurity.
Two people were killed in a gun battle in Mieh Mieh camp on Saturday.
Mr Zaki also visited the camp on Monday but was not caught up in the attack.
Palestinian sources in Lebanon say they believe the bomb was aimed at the leader of the Palestine Liberation Organisation (PLO) in Lebanon, the BBC's Natalia Antelava reports from Beirut.
However, Mr Zaki left the camp earlier than scheduled and the explosion killed Mr Medhat instead, the sources say.
"The bomb was apparently hidden in a little shed on the side of the road and was detonated as Medhat's convoy drove by," a Lebanese army spokesman told AFP news agency.
The force of the blast tore through the Mercedes in which Mr Medhat was travelling and threw the car into a nearby field, witnesses said.
Witnesses said the bomb blast could be heard across Sidon. Young Palestinian men ran to attend to casualties as ambulances and emergency workers sped to the scene.
Munir Maqdah, in charge of security at Lebanon's 12 refugee camps, said the bomb had gone off near the entrance to the camp and an army checkpoint.
Reuters news agency reported that the bomb had been planted under a manhole cover.
Mr Medhat had been visiting Mieh Mieh in an effort to calm the situation after the weekend shootings, a PLO official told AFP.
"He was on his way out of the camp where he had visited officials in a bid to ease the tension," said Hisham El-Debsi.
Osama Hamdan, a representative in Lebanon of the Palestinian group Hamas, confirmed that the dead man had played a role in helping to ease tensions among Palestinian groups.
Mr Zaarir of Fatah said the killing of his colleague was an attack on "the stability and the efforts which are being exerted in order to reunite the Palestinian factions... in Lebanon".
Palestinian Authority President Mahmoud Abbas condemned the killing as an act of terrorism, Reuters added.
"President Abbas condemns the terrorist crime that targeted Maj Gen Kamal Medhat," a statement issued by his office said.
"He dedicated his life to serve his people and his cause."
Initial reports of the attack said four people were killed along with the PLO official.