United Nations human rights experts have called on Uganda to drop charges against activists and opposition supporters arrested ahead of next month's presidential election.

They said the security forces had used excessive force during political protests and rallies.

The leading opposition candidate, the pop star Bobi Wine, said one of his bodyguards was killed on Sunday when he was run over by military police.

More than 50 people were killed and nearly 600 arrested during political protests last month.

President Yoweri Museveni is running for a sixth term in office in January's poll.