The top United Nations human rights official asked Sri Lanka's government on Tuesday to quickly locate thousands of civilians reported missing during the country's civil war. The government has said most are probably dead.

Many ethnic Tamil civilians have not been heard from since they were taken from their homes by police or military personnel or abducted by pro-government militias during the war, which ended in 2009.

Tamil politicians have handed over a list of more than 4,000 people reported missing to visiting U.N. High Commissioner for Human Rights Zeid Ra'ad al-Hussein, with the dates and locations they were last seen.

Prime Minister Ranil Wickremesinghe said last month that most of those reported missing whose names are not in the government's database are probably dead.

Zeid said Tuesday that families who were hopeful of locating their kin were distressed by the prime minister's comment.

"The statement must be followed by rapid action to identify precisely who is still alive and who has died or been killed, properly account for their deaths — including whether or not they were lawful — identify the location of their remains, and provide redress," Zeid said.

He concluded a four-day visit to Sri Lanka during which he reviewed the country's efforts to investigate allegations of wartime abuses by government soldiers and ethnic Tamil rebels, and relief for war victims.

The U.N. Human Rights Council adopted a resolution last year in which Sri Lanka agreed to investigate allegations of abuse with foreign participation.

Zeid said despite some positive developments there has been an erosion of confidence in the government's reform pledges in the Tamil-majority north and east.

He said downsizing the military to a level that is "less intrusive and intimidating" and quickly releasing private land occupied by the military would help reverse the trend.