Lebanon's deeply divided politicians united in mourning Friday for a top general whose death in a car bombing has raised fears that even the respected military has become a target in the country's unending political turmoil.

Schools and business closed as Lebanese staged a momentous farewell for Maj. Gen. Francois Hajj, who was killed along with his driver Wednesday.

Authorities were looking into the possible involvement of al-Qaida-inspired Sunni Muslim extremists seeking vengeance against Hajj, who had led a major offensive against Islamic militants last summer.

In pouring rain, his casket was first taken from the military hospital to his house in suburban Baabda, minutes away from the site of Wednesday's bombing. Hundreds of Lebanese lined up along the procession route.

An army honor guard played somber music as the flag-draped coffin was then brought to the Maronite Catholic basilica in the Christian mountain heartland north of Beirut for an official service. The casket was to be later driven halfway across the country for burial in Hajj's southern hometown of Rmeish, near the border with Israel.

The service was attended by pro-government and opposition politicians, Christian and Muslim. The opposition Hezbollah group sent a delegation.

His slaying came as Lebanon is embroiled in the latest chapter of its yearlong crisis — a dispute over electing a new president. The post has been left empty since Emile Lahoud's term ended Nov. 23, with supporters of the Western-backed government and the opposition, led by pro-Syrian Hezbollah, unable to agree on a successor.

A bishop read a message from Pope Benedict XVI, condemning the "unjustified violence" and calling on Lebanese politicians to reconcile.

The military chief of staff, Maj. Gen. Shawki Masri, promised in a eulogy the army would "not rest until the murderers are apprehended and punished" and called on the government and opposition to set aside their differences and work to end the political deadlock.

"In unity, we will have the strength and we can achieve the impossible," said Masri, the highest-ranking Muslim officer from the Druse sect.

Four Lebanese were detained Wednesday in the southern city of Sidon after the car used in the bombing was found to be registered in their names, a security official said.

Hajj was credited with crushing al-Qaida-inspired fighters known as Fatah Islam who had barricaded themselves in a northern Palestinian refugee camp, Nahr el-Bared, for three months. Hundreds of militants, as well as 168 soldiers, were killed in the fighting, which ended in September. The leader of Fatah Islam escaped the siege.

Lebanon has been shaken by a string of assassinations since 2005, but Hajj was the first military figure to be killed in such an attack.

The military is widely regarded as the only institution holding the country together. But Hajj's assassination in the high-security Baabda area — where the Defense Ministry and the presidential palace are located — underlined fears that nobody was immune from the violence.

President Bush condemned the assassination and took a tough tone against Syria, calling on it to stop interference in Lebanon — although he did not accuse Damascus in the slaying.

Some anti-Syrian politicians accused Damascus of being behind the bombing to scuttle the presidential election, but muted their rhetoric after Suleiman called on Lebanon's divided factions to avoid "politicizing" Hajj's death.

Syria controlled Lebanon for 29 years until its troops withdrew in 2005.

Army commander Gen. Michel Suleiman has emerged as a consensus candidate to become the next president, but his election has been held up by political wrangling in parliament. Hajj was a front-runner to succeed Suleiman as head of army.