The South African sporting community is in mourning after learning of the death of former Blue Bulls and Springbok flank Ruben Kruger.

Kruger has lost his 10-year battle with brain cancer, which was first diagnosed in 2000.

In a heartfelt message the Blue Bulls Company (Pty) Ltd, the players and coaches as well as the thousands of Bulls supporters expressed their condolences and sympathy with Kruger's family and friends.

The tough as nails flank was generally regarded as one of the best players that ever represented the Bulls and Boks, and his death has been described as a "massive blow" for the rugby community.

"Apart from his rugby playing abilities, he has been a superb human being and everyone that knew him will surely miss him in the months and years to come," the Blue Bulls said in a statement.

"In times like these we need one another and we trust that the Lord will comfort his family in a way that only He can."

Kruger, who played 36 Tests between 1993 and 1999, passed away on Wednesday night.

Nicknamed the 'Silent Assassin', he was also a member of the victorious 1995 World Cup Bok squad - the team famously called AmaBokoBoko, having played a major role in uniting the country just a year after South Africa's first democratic elections.

Kruger was named South African Player of the Year in 1995.

Kruger, who would have turned 40 on March 30, was diagnosed with a brain tumour soon after his playing career ended in 1999.

After the initial operation in 2000 to remove the tumour seemed to be a success, Kruger discovered a few years later that the tumour had resurfaced, but battled on against it with a strength that was a hallmark of his playing days.

He was in the news again early in 2009, when he had to be airlifted from Bloemfontein after feeling ill while returning with his family from holiday in Herolds Bay.

A five-hour operation followed, where doctors said they had removed '90 percent' of the tumour in the operation. The tumour was described as "the size of a man's fist".

Sadly for Kruger, the tumour was too sensitively placed to completely removed, and it resurfaced in June 2009 when he blacked out while driving and was involved in a car accident.

This past week Kruger began feeling unwell again and was admitted to hospital.

Funeral arrangements will be announced at a later date.

Kruger leaves behind his wife Lize and two daughters, Zoe (7) and Isabella (4).