The 27-year-old, who signed a four-year deal to switch from Bayer Leverkusen to play for Rafael Benitez's team, scored either side of half-time and was a constant threat to the Bremen defence on his debut in the famous red shirt.

Liverpool, the 2005 European champions, warmed up for the game in Grenchen, Switzerland, with two friendly wins over British minnows Wrexham (3-2) and Crewe (3-0), but were rarely troubled by Bremen.

As well as Voronin, Benitez gave debuts to new summer signings Fernando Torres, signed from Atletico Madrid, and Ryan Babel, from Ajax Amsterdam.

The game got off to a lively start as Voronin showed great finishing by intercepting a pass and rounding Bremen goalkeeper Tim Weise to slot into the back of the net to give the Reds a lead after just three minutes.

But Bremen were back level three minutes later when a shot clipped the post and forward Kevin Schindler headed home on six minutes.

Liverpool's Norwegian midfielder John Arne Riise put the visitors ahead when his long-range powerful free-kick beat Weise on 13 minutes as the Reds went 2-1 up.

Early in the second-half, Voronin clipped the cross bar with his shot, but he made no mistake later on with a well-struck shot on 61 minutes to seal the win.

The Ukrainian made way for Liverpool's new signing Torres to make his debut soon afterwards as Bremen pulled a late goal back when substitute Frank Loening saw his shot deflected into the net by Liverpool's Stephen Darby on 81 minutes.