Holmes met Foreign Minister Rohitha Bogollagama after the Tamil Tiger rebels suffered a series of defeats that have left their decades-long campaign for an independent Tamil homeland in tatters.
"I call on both sides, the government and the LTTE (Liberation Tigers of Tamil Eelam), to ensure civilians are left alone," Holmes told reporters as the military pushed ahead with its offensive to finally crush the rebels.
"I hope to hear no more of shootings of people trying to leave or recruitment of children as soldiers," he said, referring to UN reports of Tigers firing at those who try to escape from the remaining rebel-held areas.
A foreign ministry official said Holmes was expected to travel to the northeast of the island to inspect government-run relief centres for non-combatants who have fled across the frontlines.
Holmes' three-day visit came as the International Committee of the Red Cross reported an "unfolding catastrophe" with trapped civilians short of food, medicine and she