A court in Turkey's Kurdish-dominated southeast on Monday remanded in custody two British journalists working for US-based media outlet Vice News on terror charges, in a case that has sparked fresh concern about press freedom.

The two British reporters and their Iraqi translator have been charged with "engaging in terror activity" on behalf of the Daesh extremist group, the court in Diyarbakir said.

A fourth suspect, their driver, was allowed to go free, an AFP correspondent reported from the court.

They have now been taken to a jail in Diyarbakir ahead of an eventual trial. There were no further details over the evidence of their alleged links to IS jihadists.

The reporters were detained last week covering unrest in southeast Turkey which has raged as the government presses a military offensive against Kurdish rebels.

They had earlier been questioned by prosecutors who ruled to take the case to court.

The four men, including the driver, had been held in police custody since their detention last week.

Reports said that they were arrested after police acted on a tipoff and confiscated the footage shot during their reporting. All have denied the accusations in the presence of their lawyers.

Vice News, an Internet-based channel which produces in-depth video reports, named the two British journalists in a statement as Jake Hanrahan and Philip Pendlebury.

It also said that while sources initially said they were detained for filming without government accreditation, they had then been "accused of supporting the so-called Islamic State (IS)."

A Vice News spokesperson said the journalists will "face unsubstantiated charges of terrorism".

The team had been visiting the region as the government wages a relentless campaign against Kurdistan Workers' Party (PKK) militants, with several local Kurdish officials arrested and accused of supporting declarations of self rule.

Amnesty International has called for the release of the journalists, calling the accusations against them "outrageous and bizarre".

"This is yet another example of the Turkish authorities suppressing the reporting of stories that are embarrassing to them," said Andrew Gardner, Amnesty International’s Turkey Researcher.

"They should release the journalists immediately," he added.

There has been growing concern about deteriorating press freedoms on Turkey under President Recep Tayyip Erdogan and in particular over the numbers of journalists facing legal proceedings on accusations of insulting top officials.

"Authorities ought to protect —- not gag —- journalists on the job," said Nina Ognianova of the Committee to Protect Journalists.