Wall Street Journal Editor-in-Chief Emma Tucker told staff in a memo Thursday that she was "very concerned" for the safety of -based reporter Evan Gershkovich, who was arrested Wednesday by security forces in the city of Yekaterinburg.

"I am very sorry to let you know you that one of our reporters Evan Gershkovich was yesterday detained outside Moscow according to a statement put out by the Russian security services," Tucker wrote in a memo to newspaper staff at 5:11 am ET and later obtained by CNN.

"We are very concerned for the safety of Evan and will keep you informed of the situation," Tucker continued.

Gershkovich was arrested in Russia on suspicion of espionage, the first time a US journalist has been detained on accusations by Moscow of spying since the Cold War.

In a statement, the Wall Street Journal said it "vehemently denies the allegations from the FSB and seeks the immediate release of our trusted and dedicated reporter, Evan Gershkovich."

"We stand in solidarity with Evan and his family," the newspaper said. A person familiar tells CNN that the Journal is in contact with the family about the matter.

Almar Latour, the CEO of Dow Jones, which publishes The Wall Street Journal, condemned Russia's arrest of Evan Gershkovich in a memo to staffers Thursday, saying the company is working "around the clock" to secure his release.

"This is an incredibly disturbing development," Latour said in a memo to staff obtained by CNN.

"Dow Jones and The Wall Street Journal stand with Evan and his loved ones in seeking his immediate release," Latour continued. "We also vehemently deny the claims made by Russian officials."

"No reporter should be detained for simply doing their job and our team continues working around the clock in seeking his safe and swift release," Latour added. "The safety of our journalists remains our top priority."

Latour said Dow Jones is "thankful for the outpouring of support for Evan and The Wall Street Journal from readers, colleagues in the news business and many others."

The New York Times said in a statement Thursday that it is "deeply concerned" by the arrest of Wall Street Journal reporter Evan Gershkovich in Russia.

"Evan is a former Times employee whose coverage of Russia for the Wall Street Journal has been unfailingly fair and accurate," a spokesperson for The Times said. "We urge his immediate release. As we have seen too often, the arrest of journalists anywhere in the world deprives the public of news that is essential to all of us."

The New York Times said it currently has no reporters inside Russia.

The National Press club on Thursday called on Russia to immediately release Gershkovich, calling his detention "unjust," and is also urging action from the State Department.

"Evan Gershkovich is a journalist. He should be released immediately and unharmed and allowed to return to his important work," said Eileen O'Reilly, president of the National Press Club, and Gil Klein, journalism president of the National Press Club, in a statement.

The group, described as a global organization for journalists, said that in addition to considering this an unjust detention, it's calling on the State Department to "designate his detention in that manner at once."

CNN has contacted the U.S. State Department for comment. The U.S. government was informed of the arrest of Gershkovich by the Wall Street Journal, according to a U.S. official. The Journal declined to comment.

CNN's Kristina Sgueglia contributed to this report