Under tight security, the three-hour protest passed without violence, but demonstrators vented their anger, holding up large posters of Rabbani, the government’s top peace negotiator, and chanting “death to Pakistan, death to the Taleban.”

They blamed Pakistan’s military-led Directorate of Inter-Services Intelligence (ISI) for involvement in Rabbani’s killing and accused it of colluding with the Taleban to destabilize Afghanistan and derail a fledgling peace process.

“ISI and the Taleban are behind the killings of our leaders including the assassination of Professor Rabbani,” said university student Ahmad Tameem, 26.

“We will seek revenge and we want our government to break ties with Pakistan,” added Tameem, holding aloft a poster of Rabbani, who was the most prominent surviving leader of the ethnic Tajik-dominated Northern Alliance of fighters and politicians.

Rabbani was killed in his Kabul home last Tuesday by a suicide bomber posing as a Taleban envoy carrying a message of peace form the group’s senior leadership. The bomb was hidden in the man’s turban and was detonated when he embraced Rabbani with a hug.

Afghanistan’s National Directorate of Security (NDS) said on Monday it had arrested a key figure in the assassination and suggested the Taleban’s senior leadership, the Quetta Shoura, may have been involved.

It said it would recommend to President Hamid Karzai during a meeting on Tuesday to take the investigation beyond Afghanistan’s borders, where it said Rabbani’s assassination had been plotted. The NDS did not elaborate.

Many protesters were former Northern Alliance fighters and students of Kabul University. Dozens of armed police stood guard and blocked off streets with vehicles as the crowd marched.

The protest was organized by Amrullah Saleh, the former NDS chief, who stepped down last year in protest at the government’s efforts to negotiate with the Taleban which he said was a disgrace.

Saleh was a close aide to Rabbani and former mujahideen commander Ahmad Shah Massoud, who was assassinated a month before the decade-old war began.

The demonstration came amid heightened tensions that have brought fears of worsening ethnic rifts among Afghans fighting the Taleban-led insurgency.

There were angry scenes at Friday’s burial of Rabbani, when scores of supporters charged through iron gates and chanted angrily at Karzai and his government for failing to tackle the insurgency and prevent the former president’s killing.