(CNN) -- Australian Prime Minister Kevin Rudd called for calm Wednesday, assuring the Indian community that his country was still one of the safest study destinations in the world despite a series of attacks on Indian students in Sydney and Melbourne.

Australia insists the attacks are not racial, but rather "a regrettable part of urban life," as Rudd put it in a radio interview on Wednesday.

Authorities say the Indian students are victims of opportunistic criminal gangs.

"Quite often, they are catching trains home from work late in the evening as many do not have access to cars," said Simon Overland, chief commissioner for the Victoria state police. "They are often traveling alone and this is leaving them vulnerable to crime."

The Indian community, however, alleges gangs are specifically targeting Indians. Activists say there have been about 1,500 attacks a year for the last three years -- but lately, they have picked up.

"Initially, it used to be beating. Now people are being stabbed," said Gautam Gupta, founder of the Melbourne-based Federation of Indian Students in Australia. "The innovation in crime is very disturbing."

More than 80,000 Indians study in Australia, and the attacks have sparked a diplomatic dustup between the two countries

"I have been appalled by the senseless violence and crime. Some of it is racially motivated against our students in Australia," said Indian Prime Minister Manmohan Singh in a speech to the parliament.

Saying that they are tired of waiting for the Australian government to take action, Indian students -- armed with bats -- patrolled subway stations in the worst-affected suburbs Monday and Tuesday night.

Monday night, flag-waving Indians attacked a carload of Lebanese men in retaliation for the alleged assault of two Indian men by a group of ethic Lebanese earlier in the day.

Rudd urged students not to take the law into their own hands, saying "everyone needs just to draw some breath on this."

"It's unacceptable for anyone to commit an act of violence against any student of any ethnicity anywhere in Australia," Rudd said in the interview with the station 3AW. "But it's equally unacceptable for so-called 'reprisal attacks' and for so-called 'vigilante' action as well."

In response, Victoria police announced a major crackdown Wednesday, with beefed-up police presence around train stations.

"We have certainly not been sitting on our hands with this issue," Overland said. "This is not something new, but instead an enhanced approach."

CNN's Saeed Ahmed contributed to this report.

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