CAIRO - The Egyptian army called Wednesday for an end to the massive demonstrations that have shaken President Hosni Mubarak's grip on power, and the atmosphere turned ominous as the anti-government crowds were confronted by angry Mubarak supporters.

The peaceful, carnival-like atmosphere that prevailed during massive demonstrations on Tuesday gave way to a tense, charged standoff between pro-democracy demonstrators and thousands of Mubarak supporters who had been bused in.

The two sides threw rocks and chunks of cement at each other, with several people reported injured. Soldiers posted around the square did not immediately intervene.

"We must leave. Egypt is divided. There will be war," one young girl wailed.

"A young man with the pro-Mubarak group sat on a railing and stared darkly at the anti-government crowds. "They will not sleep here tonight in Tahrir Square," he said.

With Mubarak promising to step down after elections this fall, military spokesman Ismail Etman said in a Wednesday morning television address that the protesters should focus on "returning normal life to Egypt."

"Your message has arrived, your demands became known," Etman said. The government-controlled station then broadcast a printed message that read: "The armed forces call on the protesters to go home for the sake of bringing back stability."

But large crowds continued to gather in downtown's vast Tahrir Square, and seemed unlikely to disband. Egyptian opposition leaders and pro-democracy demonstrators said Tuesday that they would continue to demand that Mubarak resign immediately. They were buoyed by President Obama's statement that a transition to democracy in Egypt "must begin now."

Shortly before noon Wednesday, Internet service was restored in Egypt, having been blocked by the government for several days in what turned out to be a futile attempt to prevent the demonstrations.

By mid-afternoon Wednesday, the crowd in Tahrir Square was being confronted by a distinct, apparently orchestrated burst of support for the embattled Mubarak, who throughout his tenure has been a key U.S. ally.

Thousands of supporters of the 82-year-old president were bused into what has been the central gathering place of the anti-Mubarak forces. There were also rallies in support of Mubarak overlooking the Nile River a short distance away.

Those arriving on buses in support of the president appeared to be all men - a sharp contrast to the many families, women and children participating in the much larger anti-government protests. The men rushed into the square, shouting "No to vandalism!" and began painting over anti-Mubarak graffiti with slogans like "Egypt = Mubarak."