(CNN) -- Chelsea moved a step closer to breaking Manchester United's stranglehold on the English Premier League title with a controversial 1-0 victory at home to Bolton Wanderers on Tuesday night.
Nicolas Anelka headed the only goal against his former club just before halftime to put the London side four points clear of three-time defending champions United with four matches to play.
Third-placed Arsenal can leapfrog United into second place with victory over London rivals Tottenham on Wednesday and be three points adrift of Chelsea.
Bolton, just five points above the relegation zone, were angry after not being awarded a penalty in each half for alleged handball by Didier Drogba and John Terry -- but were lucky not to concede more goals as Chelsea dominated late in the match.
"They weren't claims for a penalty," Bolton boss Owen Coyle told match broadcaster ESPN. "They were stonewall penalties. I knew it at the time.
"Didier Drogba is a world-class player, but looking at this replay he could be a world-class volleyball player.
"I've asked the linesman about [the Terry incident] after the game but he's said it hit his shoulder. He needs to take another look at that."
Chelsea boss Carlo Ancelotti chose not to comment on the incidents.
"It is not my job to judge the work of the officials," the Italian said. "It is a difficult job, sometimes they make the right decisions, sometimes they make bad decisions.
"We have to maintain this level. We are doing well, we are very focused and in a very good position, but we have a very difficult game on Saturday against Tottenham and we have to do our best to win that game."
Chelsea were less impressive in the first half, and it took until the 43rd minute before France striker Anelka broke the deadlock with a close-range header from Drogba's left-wing cross for his first goal since January.
Bolton striker Kevin Davies had told reporters before the match that his former teammate Anelka was unhappy playing with Drogba, but the duo combined well to end Wanderers' stubborn resistance.
The recalled Salomon Kalou should have made it 2-0 in the 54th minute but goalkeeper Jussi Jaaskelainen blocked the Ivory Coast forward's shot with his legs.
Davies was booked for a crude tackle on Jon Obi Mikel in the 77th minute, and Frank Lampard hit the post soon after with a fierce low shot after a clever dummy by Kalou's replacement Joe Cole.
England midfielder Cole gave Chelsea fresh impetus, with Michael Ballack heading his cross tamely at Jaaskelainen.
Terry drove a shot just wide from a corner but soon after was beaten in the air at the other end by Bolton substitute Johan Elmander -- however, the Swede's header went wide.
Cole should have doubled the lead in injury-time, but somehow stumbled over Yuri Zhirkov's low cross when it seemed easier to score.
Meanwhile, Inter Milan moved into the final of the Italian Cup with a 1-0 victory away to Fiorentina on Tuesday night, winning 2-0 on aggregate.
Cameroon striker Samuel Eto'o scored the only goal in the 57th minute to keep Jose Mourinho's team in the hunt for three trophies this season.
The Champions League semifinalists, who drew 2-2 with Fiorentina at the weekend, will face either new Serie A leaders Roma or Udinese in the title match.
Also on Tuesday, Cagliari sacked coach Massimiliano Allegri after the Sardinian team's slump to 12th in the Italian top flight following a haul of just two points from nine matches.
Allegri was voted Serie A coach of the year by his peers for guiding Cagliari to ninth place last season, but became the 16th to be dismissed this campaign.