MILAN, May 18 (Reuters) - Zlatan Ibrahimovic returned from injury to score twice as Inter Milan retained their Serie A title on Sunday with a 2-0 win at Parma, who were relegated.Inter's triumph on the final day is their 16th championship and their third in a row, but the achievement was marred by a policeman being seriously injured in fights outside the ground, media reported. Coach Roberto Mancini also did not speak to reporters after the victory, sparking fresh media speculation he would not be continuing as manager. His side won the scudetto the hard way, missing opportunities to wrap up the title the last two weekends and letting an 11-point lead in February get whittled down to one. In the end, second-placed AS Roma finished three behind Inter after drawing 1-1 at Catania, who stay up while Empoli go down despite a 2-1 win over already-relegated Livorno. Fiorentina bagged the final Champions League qualifying place ahead of AC Milan after Pablo Osvaldo's overhead kick sealed a 1-0 win at Torino. Fifth-placed Milan beat Udinese 4-1 but will not play in Europe's premier club competition next season for the first time since the 2001/02 campaign. Milan's Carlo Ancelotti has been confirmed as coach for next season despite their failure. Juventus striker Alessandro Del Piero was Serie A top scorer in a season for the first time after his double in Saturday's 3-3 draw at Sampdoria took his tally to 21, with no one on Sunday coming close to beating his mark. Sweden striker Ibrahimovic had not played for a month and a half because of a knee problem, during which time Inter had stumbled along and threatened to throw away a scudetto they had seemed to have in the bag, just like they did in 2002. The first half in Parma was scrappy with players struggling to come to terms with the wet conditions. Inter, knowing a win would be enough whatever Roma did, carved out a few half chances but only really came to life when leading scorer Ibrahimovic was introduced in the second half. The tall forward cracked home from outside the box on 62 minutes and then guided in Maicon's cross at the far post 10 minutes from time. Inter fans were banned from attending the game because of security worries but hundreds managed to enter the stadium with thousands waiting outside to celebrate. Reports said there was some fighting in the streets around the ground before kick off with coach windows broken and stones thrown at police. Italy's ANSA news service said one officer was in a serious condition in hospital with wounds to the spleen. Parma sacked former Inter coach Hector Cuper last week and handed the reins to youth team boss Andrea Manzo, knowing they had to win to have a chance of staying up. The 1995 and 1999 UEFA Cup winners fought hard and had a couple of penalty shouts, but ultimately did not do enough and go down after 18 years in Serie A. Until Ibrahimovic's first goal, Roma were heading for the title after Mirko Vucinic's superb individual goal gave them an eighth-minute lead in Sicily. However, Catania pushed hard for an equaliser and finally grabbed the goal which kept them in the top flight when Jorge Martinez bundled home five minutes from the end. Empoli, who finished seventh last season and were in the UEFA Cup this term, would have stayed up courtesy of a better-head-to-head record over Catania if Walter Zenga's side had not scored.