width=0An Australian teenage boy was sentenced to up to 13 years jail on Thursday for murdering an Indian student in 2010, an attack which ignited a diplomatic crisis and damaged the nation's international student sector, the third largest export earner.

The killing came amid a string of attacks in late 2009 and early 2010 against Indian students in Melbourne and Sydney. The violence received widespread publicity in India, with some news outlets there claiming the attacks were racially motivated.

Australian police said race was a factor in some of the assaults, but many were ordinary crimes.

Thousands of Indian students boycotted Australia in response.

The 17-year-old teenager, known as JLE as his identity can not be revealed under court orders, was 15 when he stabbed to death Indian student Nitin Garg in Melbourne in a bungled attempt to rob him of a mobile phone.

In handing down sentence, Victorian Supreme Court Judge Paul Coghlan said the murder was opportunistic, with Garg targeted as he walked home from work at night, and probably took place in less than a minute, local media reported from the court.

Although it was a very serious crime, it was committed spontaneously, said Coghlan.

Coghlan said despite the fact JLE did not intend to kill Garg, and did not even know if he had stabbed his victim, he was still guilty of constructive murder because the killing occurred in the process of committing a violent offence.

Australia's international student sector is the country's third largest export earner, behind coal and iron ore, totaling some A$18 billion in 2010. Enrolments of international students continue to tumble, dropping 9.4 percent in the last year.