Six Italian U.N. peacekeepers were injured when a bomb struck their convoy in southern Lebanon on Friday, in a rare attack against the U.N. force that coincided with rising tensions in the country.

There was no assertion of responsibility for the bombing, which targeted a logistics convoy traveling outside the peacekeepers’ area of responsibility on a stretch of highway outside Sidon, a mostly Sunni town south of Beirut. The United Nations Interim Force in Lebanon, or UNIFIL, is based in a predominantly Shiite area farther south, where it monitors a cease-fire along the Israel-Lebanon border, between the Shiite Hezbollah movement and Israeli forces.

At a time when Lebanon is embroiled in a bitter feud over the formation of a new government while also watching fearfully the unrest consuming its more powerful neighbor Syria, there were concerns that the bombing heralded a new era of instability in country that has long served as the venue for regional rivalries.

Lebanon has lacked a proper government since January, when an alliance backed by the Shiite Hezbollah movement succeeded in overturning the parliamentary majority of the pro-Western prime minister, Saad Hariri. But the new prime minister designate, Najib Mikati, has been unable to secure a consensus on a new cabinet.

Syria, historically Lebanon’s chief power broker, has a long history of using its allies in Lebanon to settle scores and project its influence, and some expressed concern that the bombing Friday was intended to remind the international community that the Syrian regime could potentially unleash even greater regional turmoil if it is threatened.

Hariri, serving as Lebanon’s caretaker prime minister, issued a statement warning “against any attempts to use Lebanon as a new arena for sending messages against the international community,” a reference to Syria and its record in Lebanon.

In Washington, State Department spokesman Mark Toner did not rule out the possibility that Syria was involved. “We can conjecture about a lot of things,” he told reporters. “Certainly we’ve seen Syria take some action in the last couple of weeks to try to deflect attention on its own situation. But I just don't know.”

The last time the U.N. force in Lebanon was attacked was in January 2008, also a time of heightened tensions. The deadliest was in June 2007, when six Spanish peacekeepers were killed in a bomb attack close to the Israeli border.