Charlie Austin has completed a move to Southampton

Southampton have completed the signing of Charlie Austin from QPR for a transfer fee of around £4m.

The striker put pen to paper on a four-and-a-half-year contract at St Mary's after passing a medical and agreeing personal terms with Saints.

Ronald Koeman said last month Jay Rodriguez's persistent injury problems could force him into the market for a new forward, and Austin's arrival gives the Saints manager a 26-year-old who scored 18 Premier League goals last season.

Austin's Rangers deal was up this summer, but as recently as December he repeated his intention to stay at Loftus Road until the end of the season.

He has now performed a U-turn, though, and sources say the Championship club are hoping to bring in a replacement before the end of the current window.

Austin has signed a four-and-a-half-year deal at Southampton

Austin has been out for a month with a hamstring injury but recently returned to training and will link up with his new team-mates next week.

He told Southampton's official website: "I'm delighted to have got it over the line so soon into January. I can't wait to get started now.

"As soon as Southampton showed an interest that was the one club I wanted to go to. You see the progression from when I was playing against Southampton for Swindon. For me, it was important to come to a club that's on the up and that's what I've got here."

Austin was out of contract at QPR at the end of the season

Les Reed, Southampton's executive director of football, said: "We are very happy to be able to welcome Charlie to the club.

"Coming after Wednesday's morale-boosting home victory [over Watford], this signing is an indicator of our intent to finish the season strongly and continue the progress we've made in the last few years.

"Charlie shares that ambition. He has a fantastic goalscoring pedigree, but remains hungry to improve and develop as a footballer - something that convinced him that Southampton is the ideal next step in his career.

Austin scored 18 Premier League goals for QPR last season

"Having had a taste of Premier League football and his first call-up to the England squad last season, he is determined to establish himself at the highest level of the game.

"Bringing Charlie here is a show of the club's commitment to its plan for future success through investment in talent with a desire to grow and develop."

Austin leaves Loftus Road with QPR director of football Les Ferdinand's best wishes.

"It's no secret that Charlie is out of contract in the summer so this is a decision made in the best financial interests of the club," he said.

"Charlie has had a significant impact on this football club in his time here and we are hugely grateful to him for his contribution during his spell with us.

"Whilst we are sorry to lose Charlie, once he expressed an interest in moving to Southampton, we could not stand in his way."

Saints legend and Sky Sports pundit Matt Le Tissier welcomed Austin's arrival at the club.

He told Soccer Saturday: "I'm absolutely delighted. Four-million quid is an absolute steal for somebody whose goals-to-game ratio is absolutely superb.

"We've got an English player down the spine of our team who's hungry and is looking to try and get into the squad for the Euros. And that makes it a fantastic signing for Southampton Football Club."