The man in charge of the United Nation's operations in East Timor has finally taken up his post, just as the UN is facing increasing criticism from the pro-independence movement there.

The UN assumed formal responsibility for the territory three weeks ago, taking over from the multi-national force Interfet.

Sergio Vieira de Mello, the new head of the United Nations Transitional Authority in East Timor, or UNTAET, arrived in Dili after a difficult period of adjustment.

Rebuilding the ruins and ending human misery will be costly, warns the World Bank

In recent days pro-independence leaders, including the man expected to be East Timor's first president, Xanana Gusmao, have accused the UN of failing to include them in the new decision-making structure. Some have even described the exclusion of pro-independence figures as a new form of colonialism.

As well as these political challenges, Mr de Mello also inherits daunting practical ones. The task of rebuilding East Timor's shattered infrastructure is expected to be long and painful.

On Tuesday the head of a World Bank mission to East Timor, Klaus Rohland, said the territory would need between $263m and $300m for medium-term reconstruction.

This is separate from the $200m already requested by aid agencies for emergency relief, including food and shelter.

East Timor's housing and infrastructure were devastated in the weeks of widespread violence and arson attacks which followed the vote on independence at the end of August.