President Reagan's chief spokesman expressed outrage Tuesday at violence against anti-government marchers in Panama and said "there are limits to our patience."

While restating that it has been U.S. policy not to intervene militarily, spokesman Marlin Fitzwater also said, "It has always been a principle that we will protect American citizens as best we can."We are all angry at this latest demonstration, at people being beaten and threatened," Fitzwater said.

"I just want to express the outrage of all of us about this incident," Fitzwater said.

He said the regime of Panamanian strongman Manuel Antonio Noriega "is showing its true colors. It is desperate and afraid of its own people and the free press."

"The people of Panama as well as the leaders arrested yesterday have demonstrated their determination to take on the Noriega regime, despite these heavy-handed efforts at intimidation," Fitzwater said.

"The thousands of Panamanians who braved tear gas, skin irritant sprays and birdshot yesterday show that intimidation will not solve Noriega's problems."

Troops firing shotguns, tear gas and water cannons routed thousands of anti-government marchers Monday, then stormed a hotel to arrest opposition activists and journalists.

Several people were injured and dozens were arrested, witnesses said, in one of the largest protests in months against Noriega.

Monday's march through the city shut down by a general strike was one of the largest protests in months against Gen. Manuel Antonio Noriega. About 10,000 people turned the city center into a sea of waving white handkerchiefs, the trademark of those demanding the strongman's ouster.

The crowd chanted "Justice!" and "Noriega, tyrant, your end is near!" as it progressed through the shopping district. More than 90 percent of the stores were closed in support of a general strike now in its second week. The strike's organizers say it will last until Noriega leaves the country.

About 1,000 marchers had set out from the meeting place, a church in the city center. Their ranks swelled rapidly with people from buildings lining the route. Those who remained in their apartments leaned out windows waving white towels, clapping and chanting.

Suddenly, panicked marchers shouted an incongruous warning.

"Smurfs! Smurfs!" they cried, pressing backward, turning and running back down the avthe avenue.

Panamanian police water cannons are inexplicably adorned with 3-foot-tall depictions of the elfin comic strip character, known in Spanish as "Pitufos." The vehicles sped toward the crowd, spraying a mixture of water and harsh irritants that blinds those it hits for up to 10 minutes.

Within minutes, the street was empty except for gas-masked troopers and a few stumbling, sputtering individuals. Police fired tear tear gas and birdshot down the avenue and side streets, even though almost everyone was in flight.