The Post said the attack lasted for some 30 minutes and affected "a number of foreign-news stories," though they did not specify which or how many.
"We’ve taken defensive measures, and at this time there are no other issues affecting the site,” said managing digital editor Emilio Garcia-Ruiz.
This makes The Washington Post the fourth news organization to publicly confirm being targeted by the Syrian Electronic Army this year.
The hacker group, which supports Syrian President Bashar al-Assad, claimed credit in April for hijacking an Associated Press Twitter account to publish a false report about a White House bombing. The false report that sent the stock market falling within seconds. Markets dropped 1 percent before correcting after the statement was retracted.
The Post says the SEA attack followed a phishing scam by an unidentified source earlier this week, which officials believe was also the SEA. The phishing attack sent emails to journalists that appeared to be from their colleagues, and which contained a link that required a login.
In a tweet Thursday morning, the SEA claimed that it hacked The Post, CNN and Time magazine “in one strike," using Outbrain, an ad network The Post and other Web publishers use.