HELSINGBORG, Sweden, Oct 18 (Reuters) - Helsingborg avenged last month's 6-1 Champions League drubbing to Rosenborg on Wednesday, beating their 10-man opponents 2-0 in group F.

Midfielder Jesper Jansson showed some ruthless finishing in the 32nd minute, firing home from 12 metres after a brilliant pass from defender Jozo Matovac.

Rosenborg defender Erik Hoftun was sent off for hacking down Brazilian substitute Alvaro Santos from behind in the 73rd minute.

Santos, whose ball skills caused havoc in the Rosenborg defence, followed up by securing victory just four minutes later, scoring on the turn from three out metres out.

Rosenborg enjoyed the lion's share of the possession but paid the price for missed chances, while Helsingborg had luck and better finishing to thank for an unlikely win.

Rosenborg created several early scoring opportunities, with midfielder Roar Strand forcing two saves from Helsingborg goalkeeper Sven Andersson in the opening 10 minutes.

The visitors, making their sixth straight appearance in the Champions League, continued to play attractive football in midfield but failed to break down Helsingborg's defensive 4-5-1 formation.