Sian Powell in Tubu, West Timor – Yosep Palbeno gestures furiously as he tells the story of how he was threatened by five armed East Timorese police officers. Barefoot and grizzled, the market farmer has a garden high in the remote hills of West Timor, on the edge of the international border between Indonesia and the East Timorese enclave of Oecussi.

Increasing violence in these frontier regions has raised the spectre of a return to the black days of 1999, when militias burned and looted with impunity in East Timor and hatred and distrust soared between the Indonesians and the East Timorese.

Although he can't read or write, the 46-year-old from Tubu village says he knows positively that his garden is in Indonesian land, not in the 3km-long no-man's land of Oelnasi valley, and certainly not in East Timor. Yet, he says, on October 15 he was threatened by five armed East Timorese police, who pointed their sub-machineguns at him and told him to abandon his garden. He shouted for help, and about 30 of his friends and neighbours arrived and began to hurl rocks at the police. Later, he says, gesturing to the misty reaches of the valley, he heard shots fired.

Yet Palbeno's first-hand account has been contradicted by a flurry of international reports describing a violent incursion by 200 West Timorese into Oecussi, where they mobbed two East Timorese policemen who were forced to fire warning shots. "No, no, no," Palbeno says. "We never went in there."

In the whirl of claims and counter-claims, in the haze of long-held anger and resentment, and amid accusations of land-stealing, the truth can be elusive. Yet at least nine violent incursions into Oecussi in the past six weeks have been documented by the UN, and the sudden spiral of cross-border animosity has given rise to fears of accelerating clashes between disaffected East Timorese and angry Indonesians.

The swell of violence spurred a series of high-level meetings between East Timorese and Indonesian officials, including the UN mission chief in East Timor, Sukehiro Hasegawa, and East Timor Foreign Minister Jose Ramos Horta, to sort out what is going on and to cobble together some solutions.

Ramos Horta has blamed Indonesia, saying publicly that all the trouble is coming from the Indonesian side. Indonesian Foreign Affairs spokesman Yuri Thamrin says there has been trouble on both sides. "It's confusion," he says. "The border is still being finalised, and the impact is on land use."

Hasegawa says the Indonesian and East Timorese security forces have agreed to keep the local people away from the contentious areas, where more than 4per cent of the border remains unresolved. The UN chief believes the tension might now be dissipating, with no ructions in more than a week.

However, the Indonesian army's Tubu village post commander, First Sergeant Suroso, says the local people are furious. He says his soldiers have found East Timorese police guarding fields in the no-man's land. "I anticipate more trouble," he says bluntly.

The East Timorese police have never been known for their professionalism or impartiality, and they have been accused of serious breaches in the past. Palbeno says the officers who called to him spoke the local language of Dawan, suggesting they might have some regional loyalties.

Palbeno just wants to go on growing his tomatoes. "I have a garden near the border, and the police came to the border fence," he says, squatting on a hill near the thigh-high wall of broken rocks that marks the limit of Indonesia. "They called to me, they asked 'why are you working here?' I answered I was working in my garden, not in the secure land (the no-man's land)."

He holds up his hands to demonstrate how two of the police officers kept their guns trained on him. "He said 'give up your garden and don't come back'," he explains, still clearly furious. "I was frightened. I wasn't on the wrong side of the fence. The police, they said 'go home'. I said I didn't want to go. They pointed their guns at me. I said, 'you can shoot me but I'm not leaving'. I shouted."

The tomato-grower lets loose an astonishing howl, the alarm call he used to call his friends and neighbours to the scene, who responded vigorously to the East Timorese police threats. "We threw rocks at them," Palbeno says.

"The Timor police kept standing in the secure area – then the soldiers came, and they left. There were shots afterwards, but I'm not sure how many."

From the Indonesian military border post of Manusasi, Lieutenant Sujatmin agrees with Palbeno's account, saying five East Timorese police travelled through the no-man's land valley and threatened Indonesian farmers on Indonesian land. "What the police officers' aim was, we're not sure; maybe they were just patrolling, but they were in the sterile area," he added.

"We could see them through binoculars. They were shouting from a small hill." He believes the East Timorese have in the past burned their own fields, in a ploy to get the UN to stay in East Timor.

Hasegawa says the local people have not been informed of the various developments regarding the border, leading to all sorts of misunderstandings. "They have not been well-oriented yet, and we are asking that the Indonesian side fully brief them," he says.

One Western expert who asked not to be named agrees that the local communities have been poorly informed, and they don't really understand that a line of poles means they will no longer be able to farm in places where they have always farmed. "The border flare-ups themselves are a major security concern," she says. "Neither East Timor nor Indonesia has the capacity or the understanding to keep citizens informed of changes. Things can easily get out of hand."

Although militias could be peripherally involved, she says, the root causes of the incidents are misunderstandings and anger regarding the land. "This is what Australia should be concerned about, because those incidents, not militias, are what is likely to make Australia have to send soldiers to Timor again," she says.

The Indonesian military is adamant the former militias are not staging a comeback. Infantry Colonel Noch Bola says from the military headquarters in the West Timor provincial capital of Kupang that the militias had been carefully watched by the military. "My district military command is always watching those former militias," he says. "We have explained to them the impact of their actions on Indonesia." However, Hasegawa says that while there is no definite proof of militia involvement, it is known that some former militias live in the vicinity of the troubled areas.

Palbeno, who says he has never even met a militiaman, says the people of his village used to farm in the forbidden valley. "In that area, we were farming," he adds. "We had trees, vegetables, cassava. Now we are upset, because the East Timorese are still cultivating the land. We can't."

Across the valley, in Manusasi – a village so remote only motorbikes can navigate the rutted tracks – the people explain how much they resent the loss of the valley. Farmer Lamber Obino says he heard the shots a fortnight ago, but he didn't run to join in. "There are soldiers, and they have forbidden us to go there," he says. "But before, Indonesians and East Timorese, we were both working there together."