The recent surge of violence in East Timor is part of a deliberate pattern to scare voters away from participating in the August 30 referendum on the territory's future status, the United Nations said on Monday.

"The pattern is to try and intimidate people away from voting either by direct threats of physical violence now or by threatening dire consequences after the vote," UN spokesman David Wimhurst said in Dili.

Over the past two weeks there had been an increase in attacks on supporters of independence by armed militias seeking to maintain East Timor's status as part of Indonesia, he said.

The violence was limiting the ability of the pro-independence National Council for Timorese Resistance (CNRT) to campaign for the vote, Mr Wimhurst said.

"The level playing field in terms of campaigning has not been successfully established in the sense that the CNRT are in many areas not able to campaign openly, so that is a matter of concern."

He said that the United Nations was also concerned that people were being driven away from the places where they had registered to vote.

The United Nations is organising the ballot, but Indonesia is responsible forensuring security. The vote has already been delayed twice because of unrest and logistical problems.

"It seems that there is an effort being made to intimidate local people ... to move refugees out, and the concern of all these people who have been intimidated is how they are going to vote if they have been forced away from their homes," he said.

Several incidents over the weekend involved threats and violence against staff of the UN Mission in East Timor.

An Australian civilian police adviser needed six stitches on Saturday after he was hit on the head by a rock thrown into a restaurant in the militia stronghold of Suai, 95 kilometres south of Dili, Mr Wimhurst said. In the town of Same, 50 km south of Dili, several of the UN's electoral officers had to be evacuated to the police station after their house was attacked on Saturday.