The police in Tanzania, on Monday arrested several opposition politicians for allegedly planning illegal demonstrations after accusing the ruling party of rigging the general election.

Special police zone commander, Lazaro Mambosasa, told journalists in the commercial capital, that among those arrested are Chadema party national chairman Freeman Mbowe and several other leading Chadema members.

“We were tipped [off] that they were organizing illegal demonstrations and persuading youths to go into the streets today,” Mr. Mambosasa said. “We did not issue a permit for anyone to hold demonstrations, so these are illegal demonstrations.’’

Chadema meanwhile said 20 senior party officials have been detained.

The arrests come after Tanzania’s two main opposition parties on Saturday called for mass demonstrations after results from the October 28 parliamentary and presidential polls were announced.

On Friday, the incumbent President John Magufuli, known as “the bulldozer” was given an overwhelming 99 percent victory.

The U.S. embassy in Tanzania said there had been credible allegations of fraud and intimidation.