Patients being evacuated from the makeshift hospital in Putumattalan. The International Committee of the Red Cross has evacuated more than 4,000 wounded and their caretakers from the war zone. However, new patients arrive at the hospital every day.

(New York) - An expected major attack following the Sri Lankan government's "final warning" to the Liberation Tigers of Tamil Eelam underscores the need for heightened measures to minimize civilian casualties, Human Rights Watch said today. The continuing laws of war violations by both the Sri Lankan army and the LTTE indicate the need for a United Nations commission of inquiry to investigate war crimes by both sides, Human Rights Watch said.

Sources in the 20-square-kilometer "no-fire zone" reported to Human Rights Watch that the Sri Lankan army is still using heavy artillery in attacks on the densely populated area and that the LTTE continues to block civilians from fleeing. There were unconfirmed reports of hundreds of civilian casualties today alone. At least 10,000 people have managed to escape in the past day, but 50,000 to 100,000 civilians remain in the conflict area under grave threat.

"The government's ‘final warning' to the Tamil Tigers should not be considered a final warning to the thousands of trapped civilians," said Brad Adams, Asia director at Human Rights Watch. "Both sides need to show far greater concern for civilians, or many more civilians will die."

Under international humanitarian law applicable to the armed conflict in Sri Lanka, both the Sri Lankan armed forces and the LTTE are obligated to take all feasible precautions to minimize harm to civilian life and property. But since January, both sides have shown little regard for the safety of civilians in the embattled Vanni region in northeastern Sri Lanka, and more than 4,500 civilians are believed to have died in the fighting, according to UN estimates. The LTTE has violated the laws of war by using civilians as "human shields," by preventing civilians from fleeing the combat zone, and by deliberately deploying their forces close to densely populated civilian areas. The Sri Lankan armed forces have indiscriminately shelled densely populated areas, including hospitals, in violation of the laws of war.

Human Rights Watch reminded Sri Lanka of its obligations under international law to investigate credible allegations of war crimes, including by members of its own forces, and appropriately prosecuting those responsible. Past Sri Lankan government investigations into allegations of war crimes have led to few prosecutions, particularly in recent years. Human Rights Watch also called on the UN Security Council to establish a Commission of Inquiry into allegations of war crimes by both sides.

"The Sri Lankan government needs to hear loudly and clearly from a concerted international community that they, just as the Tamil Tigers, will be held accountable for what happens to the civilians in the no-fire zone," said Adams. "It is high time for the humanitarian crisis in Sri Lanka to be officially taken up on the Security Council's agenda."

Individuals who commit serious violations of international humanitarian law with criminal intent - that is, deliberately or recklessly - should be prosecuted for war crimes, Human Rights Watch said. War crimes include using human shields and deliberately attacking civilians. Evidence as to whether indiscriminate attacks on civilians were deliberate or reckless would include information on the known number of civilians in the area under attack, attacks striking presumptively civilian objects such as hospitals, and a showing that such attacks occurred repeatedly.

In addition to those who ordered or executed unlawful actions or attacks, commanders who knew or should have known of war crimes being committed and failed to take measures to stop them can be held responsible as a matter of command responsibility.

"Military commanders on both sides need to be taking civilian security into account in every action they take," said Adams. "By not doing so, they are leaving themselves open to future investigations and prosecution."