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A crowd faces troops in downtown Yangon Thursday. A day later security forces clamped down.

NEW DELHI — The military regime in Myanmar on Friday tried to shut down the Internet and cell-phone service in a bid to block news and images of the third day of its violent clampdown on dissent from being sent outside the tightly controlled country.

Such images have been crucial in galvanizing international condemnation of the military's iron-fisted response to the largely peaceful protests, which pose the stiffest challenge to the government since 1988, when thousands of pro-democracy protesters were massacred.

Soe Myint, a longtime dissident and editor of Mizzima News, a Web site focusing on news from Myanmar, said although cell-phone service was disrupted some protesters had been able to use text messages to communicate.

Despite the restricted Internet and cell-phone access, photographs and video continued to trickle out Friday, showing protesters challenging and fleeing advancing riot police and soldiers amid dark fumes in Yangon, also known as Rangoon. One young man ripped open his shirt and shouted angrily at the security forces ranged in front of him, as if daring them to shoot.

Graphic footage also emerged of what appeared to be a soldier firing point-blank at a veteran Japanese photojournalist, Kenji Nagai, who was killed Thursday. Nagai was shown lying on the ground, his camera still held up in his hand, as a soldier pointed his rifle at him. Tokyo has demanded an explanation from the Myanmar government.

Nagai was one of nine fatalities acknowledged by state media during the unrest. Diplomats and activist groups in exile say the real death toll is surely higher — possibly 100 to 200 people — their bodies quickly carted away by army or police trucks to prevent an accurate count.

"We really cannot know. We may not know for some time," Myint said.

The streets of Myanmar's principal city, Yangon, were quieter Friday as the military regime confined protesting monks to their monasteries and broke up smaller crowds of demonstrators with batons and warning shots.

"There have been clashes during the day, and there have been ... running skirmishes," British Ambassador Mark Canning told the British Broadcasting Corp. from inside Myanmar, also known as Burma. "There have been several gunshots. We don't know if they caused casualties."

Information was sketchy, but Myint said there were indications Friday that security forces might be trying to minimize fatalities. "Today they apparently didn't shoot into the crowds," he said. "They used rubber bullets. But there are people who are injured. We don't have any confirmation on that yet."

U.N. Secretary-General Ban Ki-moon expressed "grave concern" about the continued crackdown. "The authorities in Myanmar must exercise restraint, engage without delay in dialogue, release detained leaders and initiate a national reconciliation process," he said.

A special United Nations envoy, Ibrahim Gambari, is expected to arrive in Myanmar today. He hopes to meet with the military regime's top leaders, a U.N. spokesman said, and also has asked to see pro-democracy leader Aung San Suu Kyi, an influential and respected opposition figure who is considered key to any solution to the conflict.

Gambari intends to urge the government to stop using force and to convey the heightened level of the world's concern about the violent crackdown. But it is not clear whether the Myanmar government accepted his visit only because of pressure from its strategic ally, China, or whether it considers the United Nations as having something to offer.

Thant Myint-U, the grandson of former Secretary-General U Thant and the author of "The River of Lost Footsteps: Histories of Burma," said that Burma's two decades of isolation makes the government very difficult to pressure or influence.

"The military leadership is quite happy with the status quo, an inert country that is not engaged with the outside world," he said.

Security forces appeared determined to keep Yangon's streets clear of protesters. They blockaded roads into the city and sealed off the Buddhist monasteries whose clerics had been spearheading the demonstrations and rallying ordinary people to their side. Scores of monks reportedly have been beaten and arrested over the past few days.

Without the leadership of the monks, who hold an exalted position in Burmese society, and with police and troops out in force, protesters gathered in significantly reduced numbers in three or four parts of Yangon, Myint said.

With the flow of information increasingly constricted, it was impossible to say with certainty what was happening in other districts in Yangon, particularly in suburbs where anti-government sentiment has run high. Myint said that some residents had dragged trees and other obstacles into the streets to hinder soldiers and vehicles.

There were reports that troops from other parts of the country were being sent to Yangon, formerly Myanmar's longtime capital and still its main city. Demonstrations against 45 years of autocratic and brutal military rule also have been reported in recent days in the second city of Mandalay and smaller towns.

Dissident groups and sources from within the country said that divisions might be emerging among the generals who form the core of the ruling junta. Speculation centers on a possible disagreement between the senior leader, Gen. Than Shwe, and one of his deputies, Gen. Maung Ae, over the use of force, with the former in favor of firing on the crowds and the latter against.

Some junior commanders are also said to have been reluctant to carry out orders to strike hard against the monks.

But the regime's tight hold on domestic media, suspicion of foreign reporters and secretive ways have ensured that little is known about what goes on in government or in the military.

The junta appears eager to keep a lid on demonstrations ahead of the imminent arrival of Gambari. Some activists abroad say that his visit could encourage more protesters to take to the streets, but others fear that the military's intimidation tactics are having their desired effect.

"The military was more brutal than we expected. They killed the monks while the world was watching," said Aung Htoo of the Burma Lawyers Council, based in Thailand. "It was a strong message from the military that they would kill anybody."