Aung Zaw said the attack on The Irrawaddy website was one of many it has faced. The attackers replaced the site's home page with a statement accusing it of supporting "Jihad and Radical Muslims."
Aung Zaw linked the attack to a recent commentary he wrote about Buddhist extremists apparently backed by undemocratic members of the military.
Myanmar, a predominantly Buddhist nation, has been grappling with sectarian violence that has left up to 300 people dead and more than 140,000 homeless, most of them Muslims attacked by Buddhist extremists.
The disruption to the site lasted several hours, Aung Zaw said. A group calling itself the "Blink Hacker Group" took credit for the attack. Attacks on sites linked to Muslims have been carried out in the group's name, but it has also taken credit for attacking Myanmar government websites.
The Irrawaddy was founded by Myanmar journalists in exile in Thailand, and its main office is in the northern Thai city of Chiang Mai.
