Sri Lankan traffic policemen on horseback parade through the streets of Colombo on November 5, ahead of the Commonwealth Heads of Government Meeting (CHOGM) on November 15.
Sri Lanka's military on Wednesday stopped scores of ethnic Tamils from entering Colombo before a Commonwealth summit as a British TV crew also faced problems traveling around the island.
Roman Catholic priest Emmanuel Sebamali, who organised the visit by minority Tamils to the capital, said their buses were stopped initially by police and later by troops who forced them to return.
"We have been forced to turn back," the priest told AFP by telephone. "They've refused to give us a reason. They just won't allow us to travel to Colombo."
The latest military action came as the Prime Minister of Mauritius, Navin Chandra Ramgoolam, joined those of India and Canada in boycotting the Commonwealth Heads of Government Meeting (CHOGM) over alleged rights abuses when Sri Lankan forces crushed Tamil rebels in 2009.
The priest said some 200 Tamils were en route to a meeting to draw attention to the plight of thousands who lost loved ones in the decades-long separatist war.
There was no comment from police or the military. The 53-member CHOGM begins on Friday in Colombo.
A group of Tamils was similarly stopped in May by authorities who cited safety reasons, saying they could be attacked by opponents en route to Colombo.
Britain's Channel 4 TV crew, who faced a pro-government protest on arrival on Monday, had more trouble traveling to the former war zone in the northeast on Wednesday.
Hundreds of pro-government activists carried placards accusing the channel of supporting the defeated rebels and blocked their train from leaving the north-central town of Anuradhapura.
Callum Macrae, director of Channel 4's award-winning documentary: "No Fire Zone: Sri Lanka Killing Fields", said police told them they must return to Colombo.
Sri Lanka grounded domestic flights during CHOGM as a security move which also impeded foreign journalists who planned to fly to Jaffna, the Tamils' cultural capital.
It takes eight hours to travel the 400-kilometres (250 miles) from Colombo to Jaffna by land while flying takes an hour.
On Tuesday hundreds of Tamils began a separate protest in Jaffna, pressing authorities to return military-occupied land.
The organiser, Sugirthan Somasundaram, said slaughtered cow heads were thrown into his home and that of another organiser on Sunday, along with a note warning them to abandon their demonstration.
They vowed to keep up the protest until British Prime Minister David Cameron visits Jaffna during his visit to attend the Commonwealth summit.
A UN panel in 2011 found that as many as 40,000 civilians may have been killed in the final months of the civil war in 2009, mostly because of Sri Lankan military action. But Colombo denies its troops killed any civilians.