Hundreds of Pakistanis, joined by dozens of American activists, have launched a motorcade "march" against US drone strikes that they hope will reach the Afghan border region in northwestern Pakistan.

The main faction of the Pakistani Taliban has denounced Saturday's protest, and it is unclear how far the protesters will get; access to the tribal areas is controlled by Pakistan's military and security agencies.

The march, in reality a long vehicle convoy, is being led by Imran Khan, the former cricket star-turned-politician.

It began Saturday morning in Islamabad and is intended to end in South Waziristan tribal region, a frequent target of drone-fired American missiles.

Khan has been a voiciferous critic of American drone strikes in Pakistan and has alleged that large numbers of innocent civilians and tribes living along the border have been killed.

The American activists are from the US-based anti-war group CODEPINK.

Drones 'terrorise' civilians

Critics of the strikes allege such attacks kill numerous innocent civilians and terrorise peaceful communities. A report released last month by researchers from New York University and Stanford University found that the drones "terrorise" civilians living in the tribal areas.

The US rarely discusses the top-secret drone programme, but American officials have said the majority of those killed in the strikes are Pakistani Taliban and al-Qaeda fighters, and that the missiles used in the strikes are very precise.

According to the Bureau of Investigative Journalism, the US has launched more than 300 drone strikes in Pakistan in the last eight years, killing more than 2,500 people in North Waziristan alone.

Some estimates say a quarter of those were civilians, including children.

The American presence has buoyed organisers behind the protest but also added to concerns that certain groups will target the weekend event.

Ahead of the march, local media carried reports of alleged suicide bombings planned against the demonstrations, and a pamphlet distributed in a town along the march route warned participants they would face danger.