Evan Gershkovich, the American reporter Russia accuses of spying, appeals the extension of his detention.

Evan Gershkovich, the Wall Street Journal reporter jailed in Russia on espionage charges, has appealed a court decision earlier this week that extended his detention by more than three months, The Journal confirmed on Friday.

Mr. Gershkovich, 31, had already spent nearly two months in Moscow’s Lefortovo jail, known for harsh conditions, when a court on Tuesday extended his detention through Aug. 30. While the decision had been widely expected, The Journal noted in a statement at the time that it was “deeply disappointed” and would continue to demand his immediate release. The appeal was filed on Thursday, The Journal said.

The White House has said that Mr. Gershkovich is “wrongfully detained,” which effectively means the United States considers him a political prisoner. Russia has so far provided no evidence to back up the espionage charges, and the United States, The Journal and several press freedom groups have vehemently rejected them as spurious.

Mr. Gershkovich’s parents, Ella Milman and Mikhail Gershkovich, were admitted to the court building on Tuesday and were able to see their son for the first time since he was arrested on March 29, while on a reporting trip in the city of Yekaterinburg in central Russia. Ms. Milman wore a button with the phrase “Free Evan” — a rallying cry of the campaign for his release.