Aid workers say many times more aid is needed to relieve the shortages of food, medicine, shelter supplies and clothing.

U.N. officials acknowledged the aid is far from adequate. Human Rights Watch said refugees in need of aid could total 70,000. A second U.N. convoy left Saturday with enough supplies for 1,100 people. 

It is only the second time Burma’s government has allowed U.N. aid to enter areas controlled by the Kachin Independence Organization (KIO).

Aye Win, a U.N. spokesman in Rangoon, said there are at least 50,000 people displaced and in need of sustained help.

“We’d certainly like the circumstances to be more permissible for further aid delivery," said Aye Win. “Once we’re able to send another convoy we’ll certainly do so.”

The burden of providing minimal aid to the refugees has fallen on the KIO and local volunteer aid groups; the KIO and government troops have had sporadic clashes in the area since mid-summer 2011.

Many villagers who feel threatened by the Burmese army crowd into churches and makeshift KIO refugee camps along the border with China.

Authorities have allowed intermittent, small quantities of international aid into government-controlled areas but previously only allowed one U.N. shipment in December to rebel territory.

Rights groups condemn the blocking of aid as a violation of international humanitarian law.

This month, Human Rights Watch released a report saying despite Burma’s recent political reforms, which have won widespread international praise, there has been no significant reduction in abuses committed by the country’s military.

The report on the conflict in Kachin included numerous accounts of torture, rape and deliberate attacks on civilians by government troops.