Liverpool stayed top of Group K in the Europa League by holding Napoli to a goalless draw in a match marred by clashes between both sets of supporters inside and outside San Paolo Stadium on Thursday.
Three people were reportedly arrested and up to 10 people injured in clashes on the eve of the match, while five police officers were hurt around kickoff time as they sought to maintain order.
On the pitch, a largely second-string Liverpool side battled to earn a point, keeping the five-time European champions unbeaten and on five points from three games.
Zenit St. Peterburg, Stuttgart, Sporting, FC Porto and CSKA Moscow all won to maintain their perfect starts but fallen Italian giant Juventus - which is in unusual territory after failing to qualify for this season's Champions League - is still without a victory in Group A after drawing 1-1 at Red Bull Salzburg.
Elsewhere, defending champion Atletico Madrid finally claimed a win in Group B, beating Rosenborg 3-0 to climb from bottom to second in the standings.
The atmosphere ahead of the match in Naples was always likely to be volatile after events of the previous night, with reports of knives and rocks being used in clashes between fans and police.
Napoli's supporters made themselves heard throughout and Edinson Cavani was the team's main threat, the Uruguay striker drawing a save out of Liverpool goalkeeper Pepe Reina and also heading wide in the second half.
Marek Hamsik had a shot cleared off the line by Liverpool defender Paul Konchesky as the English team, which rested first-team regulars Fernando Torres and Steven Gerrard, withstood heavy pressure.
Liverpool manager Roy Hodgson will be delighted to not only earn a point against a side which is fourth in Serie A but also keep his key players fresh. The 18-time English champions, who have just been taken over by New England Sports Ventures in a deal worth 300 million pounds ($477 million), are struggling in the relegation zone in the Premier League.
Napoli is level on three points with Utrecht, which conceded an own goal through defender Alje Schut to draw 1-1 at home to Steaua Bucharest.
With Paris Saint-Germain drawing 1-1 at Borussia Dortmund to relinquish its 100 percent start in Group J, there are five teams left with perfect records after three matches in Europe's second-tier club competition.
Zenit, which won the tournament in 2008 when it was called the UEFA Cup, is six points clear in Group G after beating Hajduk Split 2-0 at home thanks to goals by Alexander Bukharov and Danny.
Stuttgart also moved onto nine points as Ciprian Marica's 29th-minute goal gave the German side a 1-0 win over Getafe in Group H.
Brazilian striker Hulk scored a second-half brace for FC Porto as the Portuguese team won its top-of-the-table match against Besiktas 3-1 in Group L. Falcao opened the scoring for Porto, with Bobo grabbing a late consolation for Besiktas, which stays second in the pool.
CSKA, the winner in 2005, maintained its superb form in Group F, posting its third successive 3-0 win by thrashing Italian side Palermo away. Highly rated Ivory Coast forward Seydou Doumbia scored either side of halftime and, after Javier Pastore was sent off in the 76th minute, Tomas Necid completed the scoring six minutes later.
Brazilian-born Portugal striker Liedson scored two of Sporting's goals in its 5-1 thrashing of Ghent that puts it five points clear in Group C.
In Group A, Juventus' inauspicious start continued as it was held by Salzburg, leaving it third after three consecutive draws. The Turin side needed a 47th-minute equalizer by Milan Krasic to earn a point, canceling out the opener by Dusan Svento.
Manchester City top Juventus' group on seven points as Emmanuel Adebayor's hat trick led it to a 3-1 home win over Lech Poznan.
Atletico, which beat Fulham 2-1 in last season's Europa League final, boosted its hopes of reaching the knockout stage by routing Rosenborg, with Diego Godin, Sergio Aguero and Diego Costa all on target.
