Award-winning Philippines journalist Maria Ressa has been freed on bail after being arrested yesterday on charges of "cytber libel".

Her arrest on Wednesday follows various other forms of pressure by the Duterte government, and sparked international and local outrage.

The winner of WAN-Ifra's Golden Pen of Freedom and one of Time magazine's 'persons of the year', she spent a night in detention after plainclothes officers from the Philippines Department of Justice's National Bureau of Investigation visited the Manila office of Rappler, the website she founded.

The incident has prompted considerable media and public attention, and staff taking photographs and video were to stop, "or we'll go after you too".

The charges apparently relate to a story published in May 2012, but updated in 2014 after cyber crime prevention laws came out, said to link a businessman with human trafficking and drug smuggling.

A presidential spokesperson said the arrest did not indicate suppression of the press, and had "nothing to do with freedom of expression or freedom of the press".