When branches heaped across the dirt road made it impossible to press ahead, Eva Galabru and her team abandoned their four-wheel drive vehicle at the edge of the jungle and set out on foot.

"Listen," she said. "You hear that?"

They paused only for an instant, noting the distant hum of a chainsaw, and then quickened their pace along the rutted, red dirt track. Moments later came the crack and thunder of a falling tree. Outfitted with a global positioning device, a 32-year-old map published by the U.S. military for its bombing campaign inside Cambodia and cameras to record evidence of illegal logging, Galabru and her two colleagues marched deeper into the Preylong Forest, following the renewed call of the chainsaw.

After hiking for more than an hour, they came across more and more stumps, hulking and coated in sawdust. The chainsaw was gone but the proof wasn't. Galabru stopped in her tracks and pointed to the ground, to leaves soiled with a slick, black substance. "That's oil from their chainsaw," she said. "That's fresh."

This discovery, made earlier this month, provided fresh evidence of commercial logging in Cambodia's vanishing forests despite a moratorium on the cutting of trees. Galabru and her London-based group, Global Witness, have documented violations by companies that they say are often linked to top Cambodian officials and operate in view of forestry officers, an effort that has landed the group in a high-stakes standoff with the Phnom Penh government. Confronted with mounting criticism, Prime Minister Hun Sen has moved to sue Galabru for slander and fire the group as the country's official forestry monitor.

At the insistence of foreign donors alarmed about corruption in the forestry business, the government hired Global Witness in 1999 as an independent monitor. Now the World Bank is threatening to suspend its entire $20 million aid program for Cambodia unless the government takes dramatic steps to protect the forests, including the development of effective plans to regulate logging and a continuing role for Galabru's group.

While more than two-thirds of Cambodia was covered with forests in the 1970s, experts now say the country could be totally logged in as little as three years. According to international forestry experts and diplomats, commercial cutting has continued despite Cambodia's announcement of a temporary moratorium on logging and the transport of timber that started in January 2002.

Cambodia's lowland evergreen trees are a coveted commodity because the relatively dry climate makes the wood unusually hard. But these trees provide the canopy for other plants and animals in the forest, and forestry experts say removing the trees could irreparably harm the environment for residents and the wider southeastern region, which has already lost most of its forests.

"It's a large problem for the country. You have a population that depends on the forest for their livelihood and for the products they need to subsist. This will make people poorer," Galabru said. She added, "Deforestation leads to climatic changes, so it's essential for the region that Cambodia's forests remain."

As Galabru and her team drove north from the capital on a recent morning toward the forestry concessions in Kompong Thom province, she spotted a pair of heavy trucks parked at the Skuon road junction and ordered her driver to pull over. Her German assistant, Marcus Hardtke, 35, got out and clambered up the side of one of the rigs. He reached down and fished out a slab of fresh bark. The truck bed was littered with it.

Galabru and Hardtke had heard reports that timber companies were trucking logs from the concessions to Phnom Penh under cover of darkness and sending the rigs back empty by day. They confronted the young driver, who acknowledged he was headed back to the forest for a new load.

A little farther north, Galabru stopped at a makeshift timber depot. She and Hardtke strode through the open gate and brushed past a bewildered employee. The grounds were stacked with scores of logs.

Galabru, 31, whose mother is a prominent Cambodian human rights activist, ran her fingers across the end of a log. "The resin is still sticky," she noted.

She also noted the chainsaw marks in the timber, which she said indicated the work of professionals rather than villagers with axes.

Despite such evidence, Cambodian government officials say the rampant logging of the mid-1990s has been brought to a complete halt.

"There is no more illegal logging in Cambodia," said Ty Sokhun, head of the Department of Forestry and Wildlife. "We have brought everything under control. We have very good, fundamental conditions for sustainable forest management in Cambodia."

In an interview, Sokhun said the only cutting of trees was being done by villagers who used the timber for fishing poles, charcoal or firewood. Sokhun called Global Witness an "extremist" group that had to be fired because it destroyed the trust between the government and foreign donors. A new monitor would be named within three months, he said.

The long-simmering tension between the government and Global Witness boiled over this fall as Cambodia prepared new long-range plans for promoting sustainable forestry. When drafts were released in November, officials from Global Witness, the World Bank and other donors called them deeply flawed. Villagers were also unhappy, afraid that the plans would affect their livelihood.

The dispute culminated Dec. 5, when police were called to break up a crowd of about 175 villagers blocking the doors of the forestry department in Phnom Penh, demanding a meeting with officials. Government officials said the police merely blew their whistles to disperse the villagers. Witnesses, however, recounted officers swinging truncheons and electric batons. Galabru reported that a dozen people had been injured.

The World Bank and Human Rights Watch issued condemnations of the government's handling of the event. Hun Sen responded by announcing he would sue Global Witness for provoking the incident and exaggerating the violence. Galabru said a case was filed against her last week.

Diplomats say Cambodia may be exploiting the controversy over Global Witness to divert attention from its proposed management plans.

Ian C. Porter, the World Bank's director for Cambodia, said they will have outside experts evaluate the plans, and he insisted that Cambodia continue the independent monitoring program without interruption, either with Global Witness or another organization. He said Global Witness must stay involved in shaping forestry reforms.

If Cambodia fails to meet these conditions, Porter said it would lose two World Bank grants worth $20 million, which have already been delayed because of concerns over forestry policy.

But diplomats in Phnom Penh are skeptical that Cambodian officials will bend to the World Bank's will. "The government is willing to take its lumps on this issue because the money to be made in forestry is so large and the gains are not distributed very far beyond a small group," a Western diplomat said.

Global Witness representatives have alleged that illegal logging is being conducted by companies tied to top government ministers, senior military officers and Hun Sen's relatives. In a statement released last year, the group reported evidence of illegal logging in Kompong Thom province by the Pheapimex company, whose owner was described by Global Witness as having "very close connections to the highest levels of Cambodian government." Galabru said in an interview that another firm accused last year of illegal forestry in the province, the Malaysian company GAT International, operated under the protection of a senior army officer close to Hun Sen.

As the sound of the chainsaw drew Galabru's team through the Preylong Forest, they came upon an elderly man, In Le, bicycling along the trail. He told them he once owned 80 trees scattered around the forest. By tapping them for resin, he said, he could make about $5, enough to subsist. In recent months, he said, a logging company had reduced nearly all of them to stumps.

"There's no more trees to get enough resin. Now I need to see if I can grow crops," he said.

Half an hour later, the team reached the site of the day's cutting, where they found the pair of Cambodian workers who had felled the trees sitting alongside the trail.

They told Galabru there were nine other company chainsaws at work in the forest.

Marcus Hardtke, left, and Eva Galabru of Global Witness gather evidence of illegal logging in Cambodia's Preylong Forest.Ty Sokhun, director of the Department of Forestry and Wildlife, says the government has brought illegal logging to a halt.Galabru and Hardtke examine a stump in Preylong Forest during a recent monitoring trip. Experts now say Cambodia could be completely logged in as little as three years.