Myanmar troops are hunting down some 2,000 civilians hiding out in the jungle after being driven from their homes in a brutal offensive against the Karen ethnic minority, reports from inside Myanmar said Friday.

The troops were some four hours walk from the fleeing refugees who had split up into groups of 300 to 400 each, said a member of the Free Burma Rangers contacted by satellite telephone as he moved with one of the groups.

The Rangers, who include Western and ethnic volunteers, provide aid to some of the estimated one million people displaced in Myanmar by decades of conflict between the military regime and ethnic minorities seeking autonomy.

Recent reports from the Rangers say the offensive, the biggest since 1997, has already uprooted more than 11,000 Karen civilians in a campaign marked by the torching of villages, destruction of food stocks, killings and torture. The ruling junta denies any human rights violations, saying it’s taking military action against a terrorist group it holds responsible for a series of bomb attacks in recent months.

The fleeing civilians, pelted by rain storms, were hiding out in remote areas of the Karen State’s Mon Township, about a nine-day walk from the Thai border to which some 1,500 other displaced people have already fled, said the volunteer who demanded anonymity because of the sensitive cross-border operation.

Karen families were carrying whatever few essential possessions they could gather up before abandoning their villages. One 60-year-old women hauled a pack weighing about 60 pounds (27 kilos) and stuffed with a cooking pot, some plastic sheets, soap, rice, a torn blanket and utensils. Other women also were loaded down with nursing children strapped to their chests, he said.

Only a trickle of aid from the Rangers and other nongovernment organizations based in Thailand has reached the 11,000 displaced including some medicine for the increasing number of people suffering from malaria and other diseases.

The Myanmar army campaign has been condemned by U.S. lawmakers, British human rights advocates and others, with some calling on the U.N. Security Council to take urgent action against the country’s ruling junta.

“The longer the Security Council waits, the more villages will be destroyed and more people will die,” said Tom Lantos, the top Democrat on the U.S. House International Relations Committee, in a statement earlier this week.

“It has been clear for many years that the Karen people are facing genocide and experiencing crimes against humanity and war crimes. This latest evidence adds further weight to these charges,” said Lord David Alton, a member of the British House of Lords active in humanitarian issues.

The Karen National Union, the main Karen guerrilla organization, says the offensive, which began last November and recently intensified, may be aimed at securing the hinterland east of the country’s newly established capital of Pyinmana.

Myanmar’s military regimes, which first came to power in 1962, waged war against numerous ethnic insurgent groups seeking autonomy until a former junta member, Gen. Khin Nyunt, negotiated cease-fires with 17 of them.

But his ouster in 2004 reinforced hard-liners within the ruling junta and “resulted in increasing hostility directed at ethnic minority groups,” U.S.-based Human Rights Watch said in its 2006 report.

The KNU are the largest of the rebel groups still facing off against the regime’s 500,000-strong military.

The violence of recent years has spawned not only the internal refugees but an exodus to neighboring countries. More than 140,000 Karen and other ethnic minority people live in refugee camps inside Thailand.