NAIROBI (Reuters) - A South Sudanese newspaper editor has been arrested for writing articles that criticized the country's leaders over a flare-up in violence earlier this month, a colleague said on Tuesday after meeting security officials.

Alfred Taban, founder and editor of the privately run Juba Monitor, was detained on Saturday, drawing calls from journalists' and rights groups for his release.

"They arrested Alfred because of the two articles of 15th and 16th July in his column," Oliver Modi, South Sudan Chairperson of the Union of Journalists, told Reuters.

He quoted security officials as saying that "Alfred will be taken to the court, and let the court at the end of the day tell us who is guilty or who is not guilty". He said it was not clear when the court hearing would take place.

In the articles, Taban said President Salva Kiir and his deputy Riek Machar had been unable or unwilling to control their troops in the latest spasm of violence, in which at least 272 people were killed.

The fighting erupted on July 7 in the capital Juba between followers of Kiir and Machar, a former rebel leader who became vice president under a deal to end a two-year civil war.

Journalist rights groups Reporters Without Borders (RSF) and the Committee to Protect Journalists, as well as Amnesty International, have called for Taban's release.

"We urge the South Sudanese authorities to free Alfred Taban without delay and to ensure that his rights are respected and that he has access to a doctor," RSF said in a statement.

"This leading journalist’s arrest constitutes yet another violation of media freedom in a country that has endured extensive violations of civil liberties since the start of the civil war."

It said another Juba Monitor editor, Anna Nimiriano, had been released after questioning on Saturday.

Journalists often complain of persecution by the security services of the African state, which seceded from Sudan in 2011.

In 2015, at last seven journalists were killed in South Sudan. In the latest flare-up of fighting, another was killed in Juba.

Information minister and government spokesman Michael Makuei said he had no comment on Taban's arrest and he was not responsible for the arrest of any South Sudanese, journalist or not.

(Writing by George Obulutsa; Editing by Mark Trevelyan)