Ugandan writer and human rights activist Norman Tumuhimbise is among nine journalists arrested on charges of "offensive communication", police in Kampala said on Monday.
Tumuhimbise, who heads a local pressure group called The Alternative Movement, was due to launch his book "The Liars and Complices" on 30 March. He has recently been promoting his book, which is critical of President Yoweri Museveni.
"The police received a complaint that the group was involved in offensive communications and promoting hate speech," said Ugandan police spokesman Fred Enanga. The group was picked up Thursday night in a van by armed security guards, according to Samuel Wanda, the writer's lawyer.
"They are with the police at the Special Investigations Unit in Kireka (a suburb of Kampala) as investigations continue," the spokesman added without giving further details.
Another lawyer, Eron Kiiza, on Monday called for the release of the group in a Kampala court, saying police had also confiscated phones, laptops, recorders and cameras. Three women were among those arrested, the lawyer said.
The news of the group's arrest came just over a month after another Ugandan author, Kakwenza Rukirabashaija was exiled. The latter arrived in Germany in February after fleeing Uganda, where he says he was tortured after his arrest in a case that has raised international concern, with the European Union and the US calling for his release.
Kakwenza Rukirabashaija was arrested on 28 December and charged with "offensive communication" against Yoweri Museveni and General Muhoozi Kainerugaba in a series of tweets. In them, he called the 77-year-old general, whom many see as the successor to his father, who has been in power since 1986, "obese" and a "curmudgeon".
Recent years have been marked in Uganda by a crackdown on journalists, the imprisonment of lawyers and the muzzling of opposition leaders.