Thomas Muller, Jerome Boateng, Javi Martinez, Alonso extend Bayern deals

Bayern Munich have extended the contracts of Thomas Muller, Jerome Boateng and Javi Martinez until 2021 while Xabi Alonso has signed a new deal until 2017.

The quartet all committed their futures to the Bundesliga giants on Friday, although coach Pep Guardiola refused to confirm whether he will be leaving Bayern at the end of the season.

Guardiola said "everything will be known" after Bayern's final game of 2016 against Hannover on Saturday, though reports in Germany suggest the Catalan coach has already told the club he will leave the Allianz Arena when his contract expires at the end of the season.

Despite doubts over Guardiola's future, Bayern have ended speculation around their 2014 World Cup-winning duo as Muller and Boateng put pen to paper on new long-term deals along with Spain international Martinez.

"We're delighted these important players have made long-term commitments," chairman Karl-Heinz Rummenigge told the club's official website. "Thomas, Jerome and Javi know how to win trophies, including the Champions League. They will add quality and stability to our team in the long run."

Muller took to Twitter after the deals were announced, writing: "I'm proud and happy to tell you that I have extended my contract at Bayern until 30.06.2021."

He added: "I have the feeling and am convinced that Bayern can play very successful football over the next few years. I'm delighted about extending my contract."

Muller, 26, has been repeatedly linked with a move to Manchester United to reunite with Louis van Gaal, who brought the forward through to the Bayern first team as a youngster.

However, the striker said in October that joining the Old Trafford club was "not up for discussion" despite reports United had offered Bayern €100 million in the summer.

Former Manchester City centre-back Boateng, 27, had also been linked with a Premier League switch, with City again thought to be interested in the Nationmannschaft defender.

Boateng said: "I'm pleased and happy at the chance to extend my stay here, I'm looking forward to the years ahead and aim for continuing great success with Bayern. This is a big contract for me and I'm delighted."

Alonso, 34, joined from Real Madrid in 2014 and had been linked with a return to Liverpool, but has now decided to remain at Bayern for another year.

He said: "I'm pleased and delighted about extending my contract for one further year. My family and I are very happy in Munich, and that's the most important thing."

Martinez, 27, had 18 months left on his previous deal. The Spain international, who missed a major part of last season with a knee injury, has been at Bayern since 2013 after joining as the club's record signing from Athletic Bilbao.

The midfielder said: "I'm very happy and proud about extending my contract until 2021. We have a magnificent team. Munich is a perfect city for a professional footballer, everyone is very respectful here and it's all come together."

ESPN FC correspondent Stephan Uersfeld contributed to this report.