The 24-year-old, who was working for a magazine based in the Indian city of Chennai, was arrested on Christmas Day for photographing military installations in Sri Lanka’s north, police spokesman Ajith Rohana said.
“We deported him this evening without pressing charges,” Mr Rohana told AFP.
“But, we deleted all the pictures he had taken in the north.”
Mr Rohana said they suspected the reporter, identified as Tamil Prabhakaran, was trying to produce a documentary and write articles tarnishing the image of Sri Lanka.
Police said he had come into the country on a tourist visa and travelled to the former war zone without declaring that he was on assignment to report from the embattled area.
There is no official censorship in Sri Lanka, but foreign journalists travelling to the former conflict zone are still required to submit their passport to the military before entering, four years after the end of the war.
A British TV crew was also barred from travelling to the Jaffna area just before a Commonwealth summit in Sri Lanka last month that was dominated by a bitter dispute over war crimes.
Also in November, authorities forced out two Australian media rights activists after accusing them of entering the country on tourist visas and participating in a rights forum.
The New York-based Committee to Protect Journalists (CPJ) accused Sri Lanka of keeping up a policy of harassing independent journalists despite the end of the fighting with Tamil rebels in May 2009.
“Sri Lankan President Mahinda Rajapakse continually insists that his administration has nothing to hide, yet time and time again, we see authorities harass and intimidate journalists in an effort to prevent them from doing their work,” CPJ Executive Director Joel Simon said.
He had also called for Mr Prabhakaran’s immediate release.
Indian diplomats said they had been granted consular access to the reporter and were told earlier Saturday that he was being deported.
Sri Lanka has resisted international pressure to address allegations of war crimes committed during the military’s final push against Tamil rebels in 2009 that ended the decades-long war.
According to the United Nations and rights groups, as many as 40,000 civilians may have died as troops loyal to the mainly Sinhalese government routed the Tamil Tiger rebel movement in its last stronghold in Jaffna in 2009.
Colombo denies the allegations but has began compiling a death toll from the war.
During the height of fighting, Sri Lanka prevented independent journalists travelling to the island’s north, drawing criticism that it was a war without witnesses. (AFP)