Seventeen soldiers and policemen were killed on Saturday after a hand grenade was thrown into their truck during an ambush near the town of Baucau. The attack brings to 41 the number of people killed in the past week in what appears to be the biggest concerted offensive in many years by the pro-independence guerrillas.
The attacks coincide with a change over in the military command which, though routine, draws attention to Jakarta's continuing need to commit disproportionate resources to the territory.
Hours after the attack, the Indonesian government's military commander in East Timor formally surrendered his command after a two-year tour of duty.
The attacks over the past few days put the lie to the belief that significant Timorese resistance has ended, and mark the climax of the most violent election campaign in 30 years. The ruling Golkar party of President Suharto won 74 per cent of the votes in last Tuesday's poll - an even greater majority than expected.
However, the result was condemned by two independent monitoring organisations, and by the main opposition United Democratic Party (PPP), whose supporters rioted on the island of Madura after allegations that ballot boxes had been eliminated from the count.
A team of election monitors from the Asian Forum for Human Rights claimed that the military had interfered in polling and deplored the "atmosphere of fear" at polling stations.
The group said in a statement: "We express grave alarm that the peoples of Indonesia should suffer violations of their sacred right to vote freely without fear or reprisal."
The Independent Election Monitoring Committee said its 8,000 volunteers in 47 cities had found evidence of multiple voting, intimidation of party scrutineers, discrimination in the treatment of voters and various procedural irregularities.
"There is an indication that there was a systematic violation of the rules," the committee's chairman said.
The US State Department called on Jakarta to investigate the reported abuses. "We also believe Indonesia should move toward a political system in which the will of the people can be heard," a spokesman said.