By Shihar Aneez and Ranga Sirilal
COLOMBO (Reuters) - Sri Lanka on Wednesday banned foreigners from a former battle zone, the government said, weeks after the United Nations began an investigation into alleged war crimes in the final phase of a 26-year conflict between the army and separatist rebels.
President Mahinda Rajapaksa in August rejected entry visas for U.N. officials for the war crime investigation. His administration has said an external investigation is unnecessary and Sri Lanka can conduct its own.
"Prior permission for the foreigners to visit the north will be implemented," the government's Information Department said in a text message. "Foreigners or relevant organizations have to write to the defense ministry for approval."
It did not give any reason for the decision.
The United Nations launched its inquiry into accusations of war crimes committed by both state forces and ethnic Tamil rebels during the conflict that ended in 2009, saying the government had failed to investigate properly.
The United Nations estimated in a 2011 report that about 40,000 Tamil civilians were killed in the final weeks of the war, mostly by the army.
Rajapaksa, who is expected to run for a third six-year term in an early election next year, and his government have rejected all the accusations.
The military last week stopped foreigners from visiting the north as a "temporary measure" because of security concerns as Rajapaksa visited the region to open a railway link that had been closed for 24 years due to the conflict.
The north of Sri Lanka is predominantly Tamil and the site of much of the fighting during the war.
The government had relaxed curbs on foreigners visiting the north after the end of the war, but many foreign visitors, including diplomats and journalists, complained of scrutiny by government security agents.
Domestic media groups and non-governmental bodies dealing with issues such as human rights say their activities have been increasingly targeted since the U.N. resolution on the investigation in March.
Media rights groups say pro-government protesters and police have disrupted at least four workshops in the last five months. Political analysts say the government might be concerned that the media could help the U.N. investigation.
A Defense Ministry body that regulates non-government organizations in July banned activist groups from holding news conferences, issuing press releases and holding workshops for journalists.
(Writing by Shihar Aneez)