Police say the arrested officer was not assigned to follow Amuriat on the campaign trail, the Daily Monitor newspaper reports.
Local television channel, NTV has tweeted photos showing the aftermath of the incident.
Ugandans will next Thursday vote for a new parliament and president. President Yoweri Museveni will be seeking a sixth term in office.
United Nations human rights experts have accused security forces of using excessive force during political protests and rallies.
Last month, the bodyguard of another opposition presidential candidate, the pop star, Bobi Wine, was killed when he was run over by military police.
--BBC--