LAIZA, Myanmar: Ethnic Kachins living in makeshift camps in Myanmar described their terror at the army's use of air power during fighting with Kachin rebels seeking more autonomy, as the government said Friday that it has exercised maximum restraint.

The escalation of attacks has made the lives of a claimed 100,000 Kachin displaced since fighting began more than 19 months ago even more perilous. Many are in camps in or near Laiza, the Kachin guerrilla-held town right by the border with China.

"We are really afraid and can't sleep well at nights," said Dashi Lu, 60, from Daw Hpun Yang village, about a day's walk from the Laiza camp where she has lived for a year.

"If I were small enough, I would hide under a leaf," she said.

The government said in a statement that the army had been given orders to cease all offensives against Kachin Independence Army guerrillas, but it had to protect its soldiers after the Kachin continued to set off land mines and ambush government forces.

The Kachin, like Myanmar's other ethnic minorities, have long sought greater autonomy from the central government. They are the only major ethnic rebel group that has not reached a cease-fire agreement with elected President Thein Sein's reformist government, which came to power in 2011 after almost five decades of military rule.

More than 19 months of fighting between the two sides escalated on Christmas Day when the rebels rejected a government demand that supply convoys be allowed to reach an army base, contending that they carried ammunition that could be used to attack their nearby headquarters.

The government then used fighter planes and helicopters to mount attacks and seized one of the guerrillas' hilltop outposts.

"Now, there is intense fighting in the vicinity of the camps and everyone is fearful," said Salang Kaba Doi Pyi Sa, head of the Kachin's refugee relief committee. "If the army uses heavy artillery, it can reach the camps."

Dashi Lu, the displaced villager, said that for safety's sake, she had already a year ago fled the village home in which she had lived all her life, along with her daughter-in-law and two grandchildren. Her son is with the Kachin guerrillas and she hasn't heard from him for three months.

"I thought we were safe but these days, the military bombardments make us very fearful," she said. "There's no place for us to run again."

The government said in a statement Friday that because the guerrillas would not let the convoys through, it "had to take military action as self-defense and in order to protect the safety of lives and properties of the people, safe and smooth transportation and peace and tranquility of the region."

It added that the military had to take action but exercised "maximum restraint" in the use of force. It also said the positions from which the military dislodged the Kachin were in uninhabited territory.

Fighting initially erupted in Kachin state in June 2011 after the KIA refused to abandon a strategic base near a hydropower plant that is a joint venture with a Chinese company.

The government last month delivered an ultimatum to the Kachin to clear a road by Christmas Day so it could supply its base. The Kachin rejected the ultimatum for fear of a government attack on their own outpost.

The Kachin have been reaching out for help from the international community.

A network of Kachin support groups on Thursday sent a letter to the Geneva-based International Committee of the Red Cross to take action against the "daily escalation of attacks" by the army and to protect the Kachin civilians.

It claimed the government was utilizing Chinese airspace for its offensive, and that the Kachin could not flee to safety because China had closed the border to them, while Myanmar's government blocked relief assistance.

In Beijing, Chinese Foreign Ministry spokeswoman Hua Chunying said Friday that during armed clashes between Myanmar government forces and Kachin rebels on the night of Dec. 30, three bombs landed in the Chinese border area but did not cause casualties.

Hua added that while the Chinese government regarded the fighting as Myanmar's internal affair, Beijing still hoped that the Myanmar government would address the issue through "peaceful negotiation with relevant parties."

China is a key ally of Myanmar as the country's main aid donor and investor. But relations have cooled as Thein Sein's government has reached out to the West to help kick-start economic growth. Many Western nations have eased economic and political sanctions that were imposed against the previous military government for its repressive policies. But Kachin state's position on the Chinese border means Beijing can still exercise its influence over both sides.

The United States earlier said the use of air power in Kachin state is "extremely troubling." On Thursday, State Department spokeswoman Victoria Nuland said the U.S. is seeking clarity on the situation following conflicting statements from Myanmar authorities, and is urging both the government and Kachin representatives to stop fighting.

"Our view is that all sides need to cease and desist and get into dialogue with each other," she told a news briefing.