The United Nations' top humanitarian official has expressed 'serious concern' over lack of access to displaced needy victims of the ongoing conflict in Sri Lanka [Images].

The world body is currently supporting Sri Lankan government's relief for some 204,000 people displaced in the north and east.

"I have been shocked by the lack of access for relief agencies to civilian communities in many conflict areas," Jan Egeland, UN Emergency Relief Coordinator said.

"The parties should be reminded that they are under international legal obligations to enable unimpeded access to civilians in need of assistance irrespective of where they are or the circumstances under which they live," he told the government and the rebels.

However, aid is beginning to get through.

Over the last few days, officials have cleared some 7,500 litres of diesel fuel for transportation by the International Committee of the Red Cross/Red Crescent, along with medical supplies and UN relief items, including sleeping mats, jerry cans, soap, emergency health kits, and bed sheets.

The UN World Food Programme has also managed to send a second convoy of 14 trucks carrying 230 tons of wheat flour to the north, after conducting a food security assessment in Kilinochchi and Mullaitivu districts (Vanni) earlier this month, the first since the resumption of hostilities earlier this year.

"The United Nations and indeed the whole international community are watching the dramatic increase in violence in Sri Lanka with deep concern," Egeland said.

"All Sri Lankans benefited immensely from the ceasefire and the parties must now return to a cessation of hostilities and to resolving their differences at the negotiating table. The United Nations stands ready to help Sri Lanka in any way that the government and the parties to the conflict deem necessary to prevent violence and promote reconciliation," he added.

About 16,000 Sri Lankans have taken refuge in India, the UN estimates.