A man has been issued with an apprehended violence order after a letter was allegedly sent to Ingrid Alexandra at University of Sydney.

It is understood security staff for the Norwegian Princess, 22, intercepted the 'suspicious' letter sent to St Andrew's College in Camperdown, where she is currently living on campus.

NSW Police attended the on-campus university residence last week to investigate the incident, the Sunday Telegraph reported.

'NSW Police issued a 63-year-old Glebe man with an apprehended personal violence order following inquiries by officers attached to Inner West Police Area Command,' a spokesperson told Daily Mail.

'No charges have been laid in relation to this incident.'

The matter has been listed for mention in Newton Local Court this Wednesday. 

The contents of the letter are unknown and it may not have been seen by the princess personally. 

However, Ingrid Alexandra's future at not only the university but also in Australia is now believed to be uncertain with rumours swirling among students she may leave. 

The princess moved to Australia to study a Bachelor of Arts degree at the university, with a focus on international relations and political economy.

She pays $45,000 a year to stay at on-campus at St Andrew’s College.

The alleged incident comes at a tough time for the Norwegian royals.

Back home, Princess Ingrid Alexandra's mother, Crown Princess Mette-Marit is 'gravely ill' with pulmonary fibrosis, a debilitating lung condition which makes it difficult to breathe. 

Her husband Crown Prince Haakon has flown home early from his official visit to Japan to be with her after the Crown Princess' condition worsened.

Ingrid Alexandra’s grandmother, Queen Sonja, 88, was also diagnosed with heart failure last week.

Ingrid Alexandra, who is second in line to the Norwegian throne, had been looking forward to her time in Australia before she arrived last August.

'It will be exciting to become a student, and I'm looking forward to gaining new perspectives on both European and international politics,' the princess posted on Instagram at the time.

'I'm sure that I will learn a lot.' 

While she has been focused on her studies, the princess has made several public appearances.

The most recent was in December, where she visited Taronga Zoo to support and learn about its wildlife animal conservation programs.   

The princess also celebrated Norway's Constitution Day at Harmony Park in Surry Hills last May alongside NSW Governor Margaret Beazley. 

A record number of Norwegian-Australians and Norwegian nationals attended the event organised by the Norwegian Australian Chamber of Commerce.