A Ugandan opposition politician vying for the presidency says the government is trying stifle his campaign after police raided his offices and arrested his staff.

Former Prime Minister Amama Mbabazi, the main rival of long-serving President Yoweri Museveni in the February elections, said Monday that 20 of his staff have been arrested.

Police spokesman Fred Enanga said arrests are related to a violent clash between Mbabazi and Museveni supporters two weeks ago. Mbabazi said his supporters were merely defending themselves. Museveni, who has been in power for 30 years and is seeking re-election, warned Sunday that police would arrest those who allegedly beat his supporters.

Amnesty International said in a report this month that the Ugandan government is reducing democratic space ahead of February polls.