(For more stories on Sri Lanka click on [ID:nSP86939])
* Military casualties: over 6,000 dead, nearly 30,000 injured
* 22,000 Tigers killed in same period - military
* Rajapaksa dismisses war crimes calls
* U.N. chief Ban flying to Colombo (Adds Rajapaksa, Ban, colour, details)
By C. Bryson Hull and Ranga Sirilal
COLOMBO, May 22 (Reuters) - Sri Lanka has for the first time made public its heavy casualties from the last phase of the 25-year war, and the U.N. chief flew to the island on Friday to push for a rapid end to a lingering humanitarian crisis.
Officials said over 6,000 soldiers were killed and nearly 30,000 injured since a battle in July 2006 that the military marks as the start of "Eelam War IV", the final stage of the war against the Liberation Tigers of Tamil Eelam (LTTE).
In the capital Colombo, tens of thousands of people marched through the streets on Friday to parliament’s grounds for a rally called to honour soldiers.
President Mahinda Rajapaksa, speaking to the assembled throng, brushed off Western calls for a war crimes probe into acts by both sides in the final months of the war.
"Since (the July 2006 battle at) Mavil Aru, 6,261 soldiers have laid down their lives for the unitary status of the motherland and 29,551 were wounded," Defence Secretary Gotabaya Rajapaksa told the state-run Independent Television Network.
Troops killed 22,000 LTTE fighters during Eelam War IV, military spokesman Brigadier Udaya Nanayakkara said.
Sri Lanka declared total victory over the LTTE on Monday after killing off its leadership and remaining fighters in a climactic final battle in the northeast of the island.
Nearly 300,000 Tamil civilians who followed or were taken by the Tigers as the military relentlessly cornered them, are now in crowded displacement camps after fleeing in the final months of what was Asia’s longest modern war.
U.N. Secretary-General Ban Ki-moon, due to land in Sri Lanka late on Friday, will call on the government to allow aid agencies to have full access to the camps and push for a political solution, U.N. officials said.
The LTTE had fought to create the separate nation that it called Eelam — the Tamil word for homeland — in northern and eastern Sri Lanka
The government had previously given casualty figures only erratically, and stopped reporting them entirely last year, mindful of a public that might not stomach heavy losses.
TENS OF THOUSANDS DEAD
The United Nations this week said the conflict had killed between 80,000-100,000 people since it erupted into full-scale civil war in 1983 — including unofficial and unverified tallies showing 7,000 civilian deaths since January.
The government does not give a civilian casualty figure, but says it did not use heavy weapons in the final months and blamed the Tigers for civilian deaths. It says the United Nations numbers were inflated by the LTTE to secure pressure for a truce.
In the waning days of the war, Western governments and the United Nations human called for probes into potential war crimes and violations by both sides.
In his speech on Friday Rajapaksa said there were people who tried to stop the military campaign by threatening to bring him and others, including his brother the defence secretary, before war crimes tribunals.
"Some are trying to do this even now. But I am not afraid of walking up to any gallows, having defeated the world’s worst terrorists, and I know that I have the confidence and the strength of my people," he said.
The U.N. Human Rights Council was due to hold a special session on Sri Lanka this week.
"Where ever there are serious violations of human rights as well as international humanitarian law, a proper investigation should be instituted," Ban told reporters aboard a U.N. plane flying to Colombo.
Ban said he was confident the government would improve access to the camps, and the International Committee of the Red Cross (ICRC) on Friday said it was already improving.
"Access was restricted last weekend for security reasons, according to the authorities. We started distributing aid again in the camp yesterday," ICRC spokesman Marcal Izard said.
U.N. humanitarian chief John Holmes has said the camps are up to international standards with the exception of restrictions on freedom of movement. The military says it needs time to weed out Tiger infiltrators before it can allow that.
On Thursday, Rajapaksa told visiting Indian envoys that he planned to have most people returned to their homes within six months. [ID:nCOL432964]
Sri Lanka has committed to begin implementing devolution of political power to Tamils as laid out in the 22-year-old Indo-Sri Lanka Accord brokered by India in its first attempt to stop a war watched keenly by its own 60 million Tamils.
Sri Lankan Tamils lost the favoured status they enjoyed under the British colonial government when it handed power over to the Sinhalese majority at independence in 1948. Tamils suffered discrimination and abuse under several subsequent governments. (Additional reporting by Louis Charbonneau in Frankfurt and Stephanie Nebehay in Geneva; Editing by David Fox)