Roberto Firmino struck in extra-time to claim a first FIFA Club World Cup title for European champion Liverpool as it beat Flamengo 1-0 in Doha on Sunday (AEDT).

A tightly contested final should have been settled by Firmino long before the 99th minute, but the usually reliable forward twice missed the target when well placed.

Liverpool also had a last-gasp penalty award struck off in normal time after a VAR (video assistant referee) review, giving Flamengo, the victor over the Reds in the 1981 Intercontinental Cup final, a lifeline.

However, the Premier League leader dominated the extra period, and Firmino finally found the net to spark yet more celebrations on Merseyside.

Liverpool scored inside two minutes of June's UEFA Champions League final, and Firmino should have put it in front after just 40 seconds on Sunday (AEDT), lifting his finish over the crossbar after breaching the Flamengo backline.

Naby Keita was similarly wasteful when Jordan Henderson freed Mohamed Salah to tee up the midfielder, before Trent Alexander-Arnold drilled wide in an extremely positive start for Jurgen Klopp's side.

After toiling for the remainder of the first half, Firmino again should have netted at the start of the second, brilliantly lifting the ball over Rodrigo Caio but slamming left-footed into the left-hand post.

Salah stabbed wide as another Liverpool flurry continued, yet Gabriel Barbosa then had two sights of goal in quick succession and tested compatriot Alisson with the second.

While Liverpool was dealt a blow as Alex Oxlade-Chamberlain hobbled off after landing awkwardly, Henderson almost stole victory with an 86th-minute curling try that was touched over by Diego Alves.

There was still room for late drama before extra time, as referee Abdulrahman Al Jassim initially awarded a stoppage-time spot-kick against Rafinha for a foul on Sadio Mane, only to then assess the incident on the pitch-side monitor and reverse his decision.

It was a reprieve that lasted only nine minutes into extra-time, when Henderson set clear Mane, who squared for the composed Firmino to sit down goalkeeper Alves and rifle into the net.

Salah was denied a swift second by Alves, and substitute Lincoln should have got Flamengo back on level terms in the 119th minute, instead blazing over in front of goal to ensure Klopp's side the title.