KABUL, Afghanistan — A surging crowd of mourners on Friday kissed the coffin of former Afghan President Burhanuddin Rabbani, slain by a suicide bomber claiming to carry a peace message from the Taliban, and railed against neighboring Pakistan for allegedly fomenting conflict in their country.

The outpouring of anger at a hilltop cemetery exposed the divisions and suspicion that plague Afghanistan after years of war, and followed a stately funeral ceremony at the palace of President Hamid Karzai, who hailed Rabbani as a tireless advocate for reconciliation.

"It is our responsibility to act against those who are enemies of peace," said Karzai, urging Afghans to shun despair over the death of Rabbani in an attack at his home on Tuesday, and instead escalate efforts to bring an end to the fighting that the U.S.-led coalition seeks to exit by the end of 2014.

One by one, lawmakers and foreign envoys stepped up to pay tribute before Rabbani's casket, draped in a red, black and green national flag. A military band played the national anthem. Then the coffin was carried by uniformed servicemen with caps and white gloves, marching stiffly.

A procession of vehicles, some bearing large portraits of Rabbani, showing him dignified in robes and with a long white beard, drove up a hill overlooking Kabul, the capital. There, the observances turned unruly. Gunfire erupted briefly, possibly because guards were jittery about the possibility of an attack.

'Death to the foreign puppets'
Supporters of the former president's political faction, chanting and distraught, reached to touch the coffin.

"Death to the foreign puppets," they shouted. "Pakistan is our enemy."

Bursts of automatic gunfire briefly unsettled the capital as police fired shots into the air to disperse large groups who moved toward the burial site without having passed tight security checks.

Streets surrounding the capital's political and diplomatic heart were blocked-off and almost empty, with police, soldiers and special forces guarding the funeral procession route.

The suicide attacker who killed Rabbani had a bomb in his turban, and gained entry to the former president's home by convincing officials, including Karzai's advisers, that he represented the Taliban leadership, based in the Pakistani city of Quetta, and wanted to discuss reconciliation.

His death has reignited long-simmering ethnic tensions, stirring fears of retribution. But his supporters called for a peaceful burial on Friday.

"We will avenge the death of our leader but today, please be calm," said a man using a loudspeaker.

'A sad day'
Car windshields and walls along normally congested roads were covered with posters bearing the face of Rabbani, a former mujahedeen resistance fighter who became president after the fall of the Soviet-backed regime.

"Professor Rabbani's martyrdom is a big loss for Afghanistan and it is a sad day for all of us," said restaurant owner Mohammad Zia.

In Washington on Thursday, U.S. Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, accused Pakistan's powerful intelligence agency of backing extremists in planning and executing an assault on the U.S. Embassy in Afghanistan last week and a truck bomb attack that wounded 77 American soldiers days earlier.

Mullen insisted that the Haqqani insurgent network "acts as a veritable arm" of Pakistan's Inter-Services Intelligence agency, or ISI, undermining the uneasy U.S.-Pakistan relationship forged in the terror fight and endangering American troops in the nearly 10-year-old war in Afghanistan.

"Death to the ISI," shouted mourners at Rabbani's funeral.

Pakistan rejected the American claims that it is supporting extremist attacks on American troops. Some analysts believe Pakistan seeks to bolster its influence in Afghanistan as a way to counter the regional influence of India, its longtime rival.

Pakistani Foreign Minister Hina Rabbani Khar warned the United States that it risked losing Pakistan as an ally and could not afford to alienate the Pakistani government or its people.

Pakistani Interior Minister Rehman Malik also rejected the accusations and warned against a unilateral U.S. ground attack on the Haqqanis, believed to be based in the mountains of North Waziristan.

"The Pakistan nation will not allow the boots on our ground, never. Our government is already cooperating with the U.S. ... but they also must respect our sovereignty," Malik said in an interview with Reuters this week.

Sirajuddin Haqqani, the head of a group his father founded in the 1980s, says he'd look forward to a U.S. ground attack.

"The United States will suffer more losses (in North Waziristan) than they suffered in Afghanistan," he said in the conversation with Reuters.

Still, he doesn't take chances, especially with drones overhead a constant worry -- 57 drone strikes have peppered the region so far this year, according the New American Foundation, a think tank that keeps a database of such attacks.

Some 55 members of his family, including his brother, have been killed in such attacks. According to the New American database, at least a quarter of the drone attacks since 2008 have targeted the Haqqanis.

"I always avoid traveling in a motorcade of armed fighters, as it puts your life in danger," he said, adding that is also why he doesn't wear a turban, standard head-dress for all male Afghans, or carry a gun.

Rabbani's mourners, many belonging to a political faction that opposes Karzai, gathered around the coffin as it was lowered into the ground and also lashed out at the Afghan government as well as the United States, which backs the Afghan president.

The 70-year-old Rabbani was the leader of Afghanistan's Northern Alliance, which helped overthrow Taliban rule during the U.S.-led invasion in 2001. His death deepens rifts between the country's ethnic minorities, especially between those who made up the Northern Alliance — including Tajiks like Rabbani — and the majority Pashtun, who make up the backbone of the Taliban.

Karzai, who is Pashtun, had appointed Rabbani to Afghanistan's High Peace Council, which was seeking to reconcile the nation's warring factions. It has made little headway since it was formed a year ago, but it is backed by many in the international community as helping move toward a settlement.

U.S. Ambassador Ryan Crocker was among those attending the funeral ceremony at the presidential palace. Iran's state media said Ali Akbar Velayati, a former Iranian foreign minister and confidant of Supreme Leader Ayatollah Ali Khamenei, led the Iranian delegation.

"Today we are witnessing one of the biggest and saddest events of this important political time in the history of the world," said Salahuddin Rabbani, the former president's son. He urged the Afghan government to aggressively investigate the killing.

Also, NATO forces said two service members died following a bomb attack in eastern Afghanistan on Friday. The deaths bring to 436 the number of international troops killed so far this year in Afghanistan.