"The Americans" has been picked up by FX for a 13-episode second season, network president John Landgraf said on Thursday.

The renewal comes just four episodes into the first season of the series, which premiered in January with 5.11 million total viewers to become the most-watched debut of any FX series.

Also read: Ratings: FX's 'The Americans' Debut Tops 'Sons of Anarchy,' 'American Horror Story' Premieres [5]

The series stars Keri Russell and Matthew Rhys as two KGB spies posing as a married American couple in suburban Washington D.C.

“'The Americans' has quickly established itself as a key part FX’s acclaimed drama line-up,” Landgraf said.  “Executive producers Joe Weisberg, Joel Fields and Graham Yost and their collaborators are telling riveting and deeply emotional stories and the performances of Keri Russell, Matthew Rhys, Noah Emmerich and the entire cast are simply outstanding. The show is truly worthy of its widespread critical acclaim and we are confident that its quality will continue to yield a robust and passionate audience.”

“We’re very grateful to John Landgraf, Nick Grad, Eric Schrier and everyone at FX for their unwavering support of our show,” said Weisberg, who created the show. “We’re thrilled to be able to continue writing stories for such an incredibly talented cast led by Keri, Matthew and Noah. We appreciate the support of the audience and we believe they have a lot to look forward to the rest of this season.”

“Working with Joe Weisberg, Graham Yost, Josh Brand, Adam Arkin, our writing staff, and the brilliant cast and crew has been a blast and I’m delighted we get to keep doing it," co-executive producer Fields added. "We couldn’t have made it happen without the constant support of Justin Falvey and Darryl Frank at Amblin TV, David Madden at Fox Television Studios and Eric Schrier at FX Productions and their wonderful teams as well.”

Nine new episodes of "The Americans" are scheduled to air this season on Wednesdays at 10 p.m. on FX.