Several opposition figures in Tanzania were arrested on Monday.
They were rounded-up for planning “illegal demonstrations” after accusing the ruling party of rigging the general election.
Main opposition parties on Saturday called out citizens to challenge the October 28 parliamentary and presidential election results.
President John Magufuli was declared winner on Friday.
Special police zone commander, Lazaro Mambosasa, confirmed the arrests of 20 politicians.
Mambosasa, in a chat with reporters, listed Chadema Party National Chairman, Freeman Mbowe among those in custody.
“We were tipped [off] that they were organizing illegal demonstrations and persuading youths to go into the streets today.
“We did not issue a permit for anyone to hold demonstrations, so these are illegal demonstrations,” Dpa quoted him to have said.
America said there had been credible allegations that fraud and intimidation occurred during the poll.