Bahraini authorities have detained four men on charges of defaming the Gulf Arab country's king on Twitter, Reuters reported citing the state news agency BNA.

The four men in their 20s were arrested on Wednesday, Oct 17 morning after security forces confiscated their computers and other electronic equipment, Mohammed al-Maskati, head of the Bahrain Youth Society for Human Rights said.

Criticizing King Hamad and other members of the Al Khalifa ruling family is a red line in the Gulf island kingdom.

Bahrain's public prosecution office had questioned four defendants and charged them with the "crime of insulting his majesty the king on their personal accounts on Twitter," prosecutor Ahmed Bucheeri said, according to BNA.

The defendants, who have been detained for a week, will face "an urgent trial before the criminal court", he said, but no date has been given.