Kampala: Ugandan police arrested opposition leader Kizza Besigye for the third time this month on Thursday as they broke up a new "walk to work" protest with tear gas, according to reports.

Besigye, who was briefly detained on Monday and last week in similar circumstances, has been staging twice weekly protests in which he walks to work to denounce rising fuel prices.

On Thursday, he drove half way and left his car on the edge of Kampala, with hundreds of people soon gathering in his wake, cheering, dancing and lying down on the road in front of

Ugandan President Yoweri Museveni has warned he would not allow any protest and police stepped in when the march neared Mulago hospital.

Police fired tear gas and stones were hurled back at them in a brief clash during which Besigye, who stood against Museveni in February elections, was bundled into a police van.

"He was thrown in a van and taken away," said Sam Mugumya, one of Besigye's aides. "They got him when we were in disarray."

Police confirmed they had arrested Besigye, who turns 55 on Friday, and were holding him at a police station near Makerere University.

"He is at Wandegeya police station," police spokeswoman Judith Nabakooba said.

Police arrested at least one other protester for throwing stones, beating him with batons as they loaded him on the back of a pick-up truck.

On Monday, police briefly arrested Besigye and several other opposition leaders, including the two other main candidates Museveni beat in the February polls, as another protest attempt was foiled.

Museveni comfortably defeated Besigye, his bush-era personal doctor turned perennial rival, in the elections but he has since faced mounting pressure over the spiralling cost of living.