The Egyptian becomes the fastest player to score 50 goals for Liverpool, achieving the feat in 65 games.
Barcelona went out of the Champions League in the first knockout phase on the away goals rule despite a 1-0 win over Liverpool.
Inter Milan notched up their 17th successive Serie A victory with a 5-2 win at Catania on Sunday.
Karim Benzema scored his sixth goal in four games as Real Madrid beat Alaves 3-0 on Sunday for a fourth successive La Liga victory which took the European champions to within eight points of leaders Barcelona.
A round-up of Wednesday's Champions League first knockout round, first leg ties.
Watford equalised seconds before halftime through Abdoulaye Doucoure and in a rampant spell of attacking football went ahead four minutes after the break when Roberto Pereyra tapped home a Richarlison cross.
Zenit St Petersburg and Middlesbrough dented the UEFA Cup hopes of Olympique Marseille and tournament favourites AS Roma.
Manchester United can give up hope of signing AS Roma's Dutch midfielder Kevin Strootman in the next transfer window, the Italian club's owner told the BBC on Wednesday.
'I'm very excited to be here. I'm very happy'
Chelsea secured top spot, above Barcelona, in Group A with a 2-0 home win over Levski Sofia.
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IMAGES from the soccer matches played in Spain and Italy on Saturday
Portuguese forward Cristiano Ronaldo needed to take time off and even miss games if he is to see out an arduous season after he limped off before the end of Real Madrid's 3-0 victory over Villarreal on Wednesday, according to manager Zinedine Zidane.
champions Inter Milan are now three points clear at the top of Serie A with 17 points from seven games courtesy of their 2-1 win over Napoli.
Ibrahimovic has not played since suffering a career-threatening knee ligament injury in United's Europa League quarter-final second leg match against Anderlecht at Old Trafford in April.
Inter Milan extended their lead at the top of Serie A to four points when Patrick Vieira scored the winner in a 2-1 victory at Palermo.
Champions Juventus lost for the third time in six Serie A matches this season after goals from Lorenzo Insigne and Gonzalo Higuain secured a 2-1 home win for Napoli on Saturday.
Second-placed Napoli comfortably overcame the absence of suspended top scorer Gonzalo Higuain to brush aside bottom-of-the-table Verona 3-0 in Serie A on Sunday. Napoli stayed points six behind leaders Juventus, who won 2-1 at AC Milan on Saturday, with six matches each to play, and remain outsiders to win their first title since 1990 despite the win. Higuain, who has led Napoli's challenge with 30 goals, will miss the next three games as he completes a four-match ban for his sending-off and furious reaction in last week's 3-1 defeat at Udinese. Fiorentina's recent dismal run continued when they lost to their smaller Tuscan neighbours Empoli for the first time since 1997, leaving them fifth in the table. Juventus have 76 points from 32 games with Napoli on 70, AS Roma on 63, Inter Milan on 58 and Fiorentina on 56. Napoli hit the post twice and had a goal disallowed before Manolo Gabbiandini headed them in front in the 33rd minute, his fifth goal in only seven starts this season, after Verona goalkeeper Pierluigi Gollini parried Jose Callejon's shot.
Images from football matches played across Europe on Sunday.
Egypt striker Mido has returned to Tottenham Hotspur after the club reached agreement on a deal with AS Roma.
Italy's top-flight Serie A soccer league launched a new anti-racism campaign on Monday by presenting artwork featuring three side-by-side paintings of apes but the move has been described by campaign group Fare as a sick joke. News of all that's transpired on and off the football field.
Cristiano Ronaldo was booed by Real Madrid fans despite grabbing one goal and laying on another in their 2-0 Champions League last-16 second leg win over AS Roma on Tuesday.
Zidane plays down Ronaldo injury; Liverpool's Gomez sidelined after surgey
First-half goals by Gervinho and Mattia Destro helped AS Roma strengthen their grip on second place in Serie A with a 2-0 win at Chievo Verona on Saturday.
Racing Strasbourg, bottom of Ligue 1 and without a league win this season, secured their place in the last 32 of the UEFA Cup on Thursday with a 1-1 draw at AS Roma.
The Brazilian striker said he hoped that his return to form could help push Inter Milan on towards success this season.
Francesco Totti made an instant impact on his return from a buttock injury when he scored one goal and helped set up another in AS Roma's 3-2 Serie A win over Udinese on Monday.
Chelsea beat Valencia 3-2 on aggregate to enter the Champions League semi-finals for the third time in four seasons.
He made it 3-0 with a superb first-time finish into the bottom corner in the 20th minute, scoring his first ever treble in a competitive game, more than 19 years after making his professional debut.
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Ukraine football federation president Hryhoriy Surkis said he expected Dynamo Kiev to be awarded the match.
The Champions League group stages took on a less predictable look after Thursday's draw, helped by UEFA's decision to tweak the seeding system.
Middlesbrough beat AS Roma to reach the UEFA Cup quarterfinals for the first time
2004 Champions League finalists Monaco were eliminated 2-1 on aggregate by Swiss side Basel.
Kazakhstan's Astana fought back to beat a youthful Manchester United side 2-1 at home, Arsenal's woes continued as Frankfurt's Daichi Kamada scored twice to secure a 2-1 win.
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