Story highlights Authorities block road into South Waziristan, ending protest march

Leader says the march still achieved its goal of drawing attention to drone strikes

Officials say demonstrators were kept out of South Waziristan for security reasons

March was led by former cricket star turned politician Imran Khan

A protest march against U.S. drone strikes in Pakistan, led by former cricket star turned politician Imran Khan, came to a halt on Sunday when authorities blocked access to the demonstration's final destination in the tribal region, officials told CNN.

Authorities used steel shipping containers and security forces to seal off the road entering South Waziristan, where protesters had planned to hold a rally on Sunday, local government official Shahid Ullah said.

When confronted with the roadblock, Khan directed protesters to turn back, saying the march had achieved its goal of drawing attention to the controversial U.S. drone strikes.

Khan has been a fierce critic of U.S. policy in Pakistan and the use of drone strikes, calling them a violation of Pakistan's sovereignty and a strategy that fuels militant anger towards Washington.

"We will not cause any trouble if the government doesn't want us to enter South Waziristan," Khan told reporters. "We just want to direct the attention of the entire world to these illegal and immoral drone attacks in Waziristan that have left many innocent people dead."

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In recent years Washington has sharply stepped up the use of drone attacks in Pakistan's mostly ungoverned tribal region, widely believed to be a safe haven for militant groups fueling the insurgency in Afghanistan. U.S. officials say the drone strikes are an effective strategy against militant groups and insist civilian casualties are rare.

The anti-drone march set out in a convoy of more than 100 vehicles from the capital, Islamabad, on Saturday and reached the border of South Waziristan on Sunday afternoon, where it was turned back.

The U.S.-based anti-war group Code Pink was part of the procession. Throughout the journey the pink-clad peace activists regularly chanted anti-drone slogans in Pakistan's native language of Urdu.

"Stop them! Stop them! Stop the drone attacks," the protesters shouted in Urdu.

Pakistani authorities had earlier warned that the demonstration would not be allowed to enter South Waziristan for security reasons.

"The situation in the tribal areas is comparatively good but not suitable for any gathering there," Tashfeen Khan, a government official, said on Saturday.