Tanzanian authorities said Friday they are holding an opposition figure who is accused of calling President John Magufuli a dictator.

Tundu Lissu of the opposition Chadema party was arrested Thursday at the airport in the commercial capital, Dar es Salaam, before he could board a plane for Rwanda, said Lucas Mkondya, the acting Dar es Salaam Special Police Zone commander.

Lissu is being questioned over making anti-government speeches that could lead to unrest, Mkondya said.

"He will not be released today," he said, adding that "it will not be tomorrow, either." Lissu has not been charged.

In a news conference Monday, Lissu rebuked the government for its alleged attacks on the opposition and the media, and urged Western donors to freeze aid to the government.

He called on the international community to treat Tanzania as the "skunk of the world."

Since his election in 2015 Magufuli has faced growing charges of intolerance for criticism in the East African nation.

Live transmission of parliamentary debates has stopped, and opposition rallies have been banned until the next election cycle in 2020.