كتب : وكالات
The in-form Cameroonian striker opened the scoring after 21 minutes when he placed the ball between keeper Tim Wiese's legs after being set up by Argentinean midfielder Esteban Cambiasso.
He doubled the hosts' advantage five minutes later after capitalizing on some poor defending.
A deft Eto'o pass allowed Dutch playmaker Wesley Sneijder to add the third on 34 minutes.
The former Barcelona man completed the rout nine minutes from time for his 11th goal in all competitions so far this season.
The only downside for Inter was the injuries defender Lucio and keeper Julio Cesar sustained in the game.
The Champions League holders top Group A with four points from two games, ahead of Tottenham Hotspur on goal difference after the English side crushed Twente 4-1.
Fellow heavyweights Manchester United enjoyed an away victory over Valencia while Barcelona were held to a 1-1 draw by Russia's Rubin Kazan.
In Valencia, Mexican striker Javier Hernandez came off the bench to strike with five minutes remaining and give United a valuable 1-0 victory.
He swept home a low cross from Federico Macheda to hand the Red Devils their second win in 19 trips to Spain in European competitions.
United are on top of Group C on four points, ahead of Scottish giants Rangers on goal difference and one point clear of third-placed Valencia.
In Russia, Barcelona fell behind to Christian Noboa's penalty after 30 minutes.
Spain striker David Villa converted another penalty 30 minutes later to level the score.
The Spanish champions were unlucky not to bag all three points after wasting a host of clear-cut opportunities.
Group D leaders FC Copenhagen, who claimed a 2-0 win at Greek side Panathinaikos, have maximum six points, two above Barcelona.
Inter 4-0 Werder Bremen