BERLIN: German champions Bayern Munich on Tuesday splashed out a reported 73 million euros ($83 million) to launch their Champions League campaign for next season by signing Germany defender Mats Hummels and Portugal teenager Renato Sanches.

Centre-back Hummels, 27, becomes the third Dortmund star to join German champions Bayern in three years after midfielder Mario Goetze in 2013, followed by striker Robert Lewandowski in 2014.

Sanches and Hummels have been given five-year contracts at Bayern, who were confirmed German champions for a record fourth season in a row last Saturday.

The team are smarting though after being beaten by Atletico Madrid in the Champions League semi-final.

Neither Dortmund nor Bayern said how much the Hummels transfer cost, but German media put the fee at 38 million euros.

The Bavarian giants confirmed they paid 35 million, plus bonuses, for the 18-year-old Sanches. Benfica said the fee could rise to 45 million euros.

Hummels and Sanches will join the Bayern squad when Carlo Ancelotti replaces Manchester City-bound Pep Guardiola for the 2016/17 campaign.

Hummels' transfer will add extra spice to the German Cup final on May 21 in Berlin when Bayern meet Dortmund in the battle of Germany's top clubs.

“My decision has not been made easier by the last eight-and-a-half years,” said Hummels, who joined Dortmund on loan from Bayern in 2008 before the transfer was formalised a year later.

Boos for Hummels

“Before I return to my hometown in the summer, we all have a great common goal: to bring the German Cup to Dortmund,” he added in a statement.

Hummels was booed and jeered by Dortmund fans 10 days ago, after reports first emerged he was set to join Bayern.

He can expect a similar treatment at Signal Iduna Park on Saturday for Borussia's final home game against Cologne.

“We respect his decision. I want to emphasise that he has behaved openly and fairly towards us at all time,” said Dortmund's CEO Hans-Joachim Watzke.

At Bayern, Hummels will pair up with his national team-mate Jerome Boateng and they were Germany's centre-backs in the 2014 World Cup campaign.

“We are delighted that Mats Hummels has opted for Bayern,” said Bayern chairman Karl-Heinz Rummenigge.

“Mats is one of the best central defenders in the world and with him, we can further increase the quality of our team. “Hummels returns to the Bavarian giants having won the German league title twice with Dortmund (in 2011 and 2012) and the German Cup (2012), as well as the 2014 World Cup.

Bayern beat off competition from Manchester United for talented teenager Sanches. The defensive midfielder has had a meteoric rise this season.

He was first capped by Portugal this year having only made his debut for Benfica in the Portuguese league last October.

“Renato Sanches has been observed over a long period of time by FC Bayern,” said Rummenigge. “We are fortunate to have signed him in spite of well-known international competition.

“Renato is a dynamic, combative and technically-gifted midfielder, who will strengthen our team further.”

Benfica announced on its website that “it has reached agreement with Bayern Munich for the permanent sporting rights to athlete Renato Junior Luz Sanches for the sum of 35 million euros”.

It added that the accord “allows for addtional sums which could take the total sum to 45 million euros depending on the achievement of specific targets”.

The contract runs until June 30, 2021.