BEIRUT: A roadside bomb blew up next to a United Nations convoy carrying French peacekeepers in south Lebanon on Tuesday, wounding at least five of them in the second attack on the U.N. force in two months, the United Nations said.

According to The Associated Press, the bomb went off at the southern entrance of the port city of Sidon as a U.N. convoy with several vehicles was passing by.

The UN Security Council called the bombing a "terrorist attack" and condemned it "in the strongest terms." It also condemned all attempts to threaten the security and stability of Lebanon.

UN Secretary-General Ban Ki-moon also strongly condemned the attack and "is deeply disturbed" at the second major incident targeting the peacekeeping force in two months, U.N. spokesman Martin Nesirky said.

It was not immediately clear who was behind the attack. But political tensions are rising in Lebanon over an UN-backed tribunal's indictment last month of four Hezbollah members in the 2005 assassination of former Lebanese Prime Minister Rafik Hariri.

Iranian-backed Hezbollah is the most powerful political and military force in Lebanon today and it has refused to hand over the suspects. The tribunal is expected to publish details of the indictments after a 30-day deadline that expires at the end of the month.

There are also concerns that unrest in neighboring Syria, which has seen more than four months of protests against the autocratic government there, could spill over into Lebanon.

UN peacekeepers have been deployed in southern Lebanon since 1978 to monitor the border with Israel. The force was boosted to almost 12,000 troops after Israel and Hezbollah fought a war in 2006. Under the UN resolution that ended the fighting, the force is monitoring a zone south of the Litani River where Hezbollah is banned from keeping weapons.

The Security Council reaffirmed its determination to ensure that no acts of intimidation prevent the UN force from carrying out its mandate to monitor the Israeli-Lebanon border.

In a similar attack about two months ago, a roadside bomb ripped through a UN convoy carrying Italian peacekeepers in southern Lebanon, wounding six. The May 28 attack was the first since 2008.

UNIFIL spokesman Neeraj Singh said five peacekeepers were injured in the latest bombing and three went to a hospital. He did not say what nationality they were, but Lebanese security officials said they were French.

French Foreign Minister Alain Juppe and the Security Council said six French peacekeepers had been wounded.

The discrepancy in casualty numbers could not be immediately reconciled.

Prime Minister Najib Mikati denounced the bombing and ordered an immediate investigation, his office said.

The Security Council welcomed the Lebanese government's commitment to launch an investigation to bring to justice the perpetrators of the attack.

The deadliest attack on UNIFIL was in June 2007, when a bomb hit an armored personnel carrier near the Israeli border and killed six Spanish peacekeepers.

No group has claimed responsibility for any of the attacks.