Cyle Larin scored a goal in each half to help Southampton thrash Millwall at St Mary's.

A deflected Mark Sykes strike put the Lions ahead early on before the Canadian headed the equaliser.

Finn Azaz struck to make it 2-1 before half-time and a Leo Scienza penalty, Larin's second, and a Tom Fellows shot wrapped up the win.

Southampton's points total is now positive as they move up to 17th with two points after beginning the campaign on minus four, while the visitors are fifth after a first defeat.

Sykes scored inside 15 minutes to give Millwall the lead, his deflected effort deceiving keeper Daniel Peretz after good work by Josh Coburn in the build-up.

Saints soon kicked into gear and Larin nodded them level 10 minutes later, meeting Ryan Manning's free-kick for his third goal of the season.

Azaz completed the first-half turnaround seven minutes before the break, but it was all about Scienza. The Brazilian's mazy run opened up the opportunity before feeding the midfielder, who applied the finish.

Kyrell Lisbie almost restored parity for Millwall with half-time looming, but struck the post from Tairyk Arconte's cross.

Scienza put the home side 3-1 up from the penalty spot on 55 minutes after Jake Cooper fouled Azaz in the area.

Larin's second just after the hour was a stunning effort, the forward flicking the ball over his head before lashing home brilliantly to put Saints in total control.

A wonderful afternoon for the home side was topped off when Fellows completed the rout four minutes from time with a tame shot which trickled over the line.

Southampton manager Tonda Eckert speaking to BBC Radio Solent: "No start to the season is easy.

"As much as we all want things to get up and running from the start, it takes time.

"We've seen in moments of the game how good we can be. Even after today there is a lot more to come.

"There is a long way to go. We managed to stay humble and hungry last year and that is the job. Tuesday's game (at Birmingham) is going to demand a lot from us.

"Today and tomorrow it is about recovery and then we will focus on that."

Millwall manager Alex Neil speaking to BBC Radio London: "My assessment is goals change games.

"For 25 minutes, I thought we were excellent. We dominated the opening proceedings and scored a good goal and probably should have scored another.

"We haven't been as clinical [as needed] and games like today show that comes back to bite you a little bit.

"I was surprised how much their first goal seemed to set us back, which I don't understand. We normally go again.

"If we scored before half-time, we could have gone again second half. The second half is difficult because we already have two forwards on the pitch.

"We are already ultra aggressive. The next goal was really important. It was disappointing."