Defending champions Arsenal took a big step toward the Women's Champions League quarterfinals by routing OH Leuven 4-0 in the first leg of their knockout playoff round on Wednesday.

In a repeat of their final fixture of the league phase, Arsenal dominated from the start in Belgium to close in on a quarterfinal meeting against London rival Chelsea.

Frida Maanum led the visitors with two goals, and Olivia Smith showed she was worth the record transfer fee Arsenal paid Liverpool for her in July. Kim Little came on as substitute to play her 400th game for Arsenal.

Maanum headed in the opener after meeting a cross by Caitlin Foord from the right in the 22nd minute.

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That settled the visitors who soon doubled their advantage through Smith, a quarter of an hour later -- a clinical finish from the Canada forward found the far corner of the net with a first-time low shot..

The third arrived early in the second half. Foord did a fine job of holding off Saar Janssen, squaring the ball for Maanum, who tapped in her second goal of the game.

Arsenal's fourth came 18 minutes from time and owed to a goalkeeping error.

Lowiese Seynhaeve got hands to Smith's cross but could only push the ball into the path of Russo, who volleyed on with her right foot.

The revamped Women's Champions League format has followed the men's competition with an opening league phase of six rounds instead of eight. The top four in the standings -- Barcelona, Lyon, Chelsea and Bayern -- advanced directly to the quarterfinals.

Teams placed fifth to 12th went to the playoffs round. Arsenal finished the league phase in fifth while Leuven was 12th in its first campaign in the European top competition.

The two met in the 18-team league phase with Arsenal beating Leuven 3-0 away.

Information from PA and AP was used in this report.