Zlatan Ibrahimovic (left) celebrates with Giacomo Bonaventura on Saturday. Photo: Xinhua

Veteran Swedish star Zlatan Ibrahimovic scored on his first AC Milan start since his return to the club in a 2-0 win over Cagliari on Saturday but city rivals Inter's position on top of Serie A is at risk after a 1-1 draw against Atalanta.

Lazio consolidated third position, four points behind Inter, with the league's top scorer Ciro Immobile grabbing the only goal against Napoli to stretch his side's winning streak to 10 games.

"We gave everything in a difficult situation," said Inter coach Antonio Conte. "We were down to the bare bones, without four big players."

Atalanta are fifth, equal on points with Roma, who occupy the final Champions League berth.

In Sardinia, Ibrahimovic was named in the starting 11 for Milan against Cagliari on Saturday, having come on as a substitute in their goalless draw against Sampdoria the previous weekend.

The 38-year-old played the entire match scoring after 64 minutes for his first Milan goal since leaving the club for Paris Saint-Germain eight years ago.

"I'll celebrate like a God at San Siro, not here," said Ibrahimovic, who last scored in the Milan jersey in May 2012. "I celebrate God every time I score, that way I feel alive!"

Portuguese forward Rafael Leao, 20, had struck the opener just after the break as Milan got their first win since a 3-2 victory over Bologna on December 8. 

Since then, Stefano ­Pioli's side have settled for two goalless draws and suffered a humiliating 5-0 defeat by Atalanta.

Milan move up to eighth in the table, 10 points off the Champions League berths.

"The coach just wanted to think about my age and see if I needed a rest, but there's no problem," said Ibrahimovic, who did not want to be substituted. 

"My brain is always the same and the body has to follow."

It was his 57th goal for the club and 123rd in Serie A, having also played for Inter Milan and Juventus. He was denied a second with eight minutes to go by the linesman's flag.

"Ibra is an important point of reference, but it will still take time to perfect," said Pioli. 

Ibrahimovic has a six-month contract with an option for another season. He helped the club win their 18th and most recent Serie A title in 2011.