Turkey's state-run Anadolu Agency says a court in Istanbul has charged three academics with making terrorist propaganda and ordered them arrested pending the outcome of a trial.

Their arrests late on Tuesday came a day after President Recep Tayyip Erdogan said Turkey should "redefine" terrorism and terrorists so that legal action can be expanded against anyone supporting terrorism — including legislators, academics and journalists.

The three Istanbul-based academics were among a group of more than 1,000 scholars who in January signed a declaration denouncing military operations against Kurdish rebels. The declaration angered Erdogan and led to legal proceedings against some.

The three were detained for questioning earlier on Tuesday for holding a news conference last week during which they stood by the declaration.