Friday was the deadline for nationals of many Arab and Muslim countries who are in the United States temporarily to register with U.S. immigration officials. An earlier phase of the program led to hundreds of detentions and sparked protests on the West Coast. As thousands registered around the United States, protesters were on hand in Los Angeles.

The registration of men aged 16 and older from North Korea and a dozen other countries is part of a post-September 11 effort to tighten security.

Abed Tabaa, a native of Syria, has been in the United States for 19 years. He is now waiting to become a permanent resident, and was one of thousands of foreign nationals who registered last month in the first phase of the program. He spent three days in detention, saying "we slept on the floor with no blanket on the cold floor, not carpet, cold floor."

At least several hundred who registered in December were detained while authorities determined their status. Lawyers for immigrant groups put the number at 1,000. Most detentions were in Southern California, and most of those detained have been released.

The registration process appeared to be smoother Friday. Immigration officials say that added personnel and a better computer system are speeding the process.

But dozens of civil liberties groups protested the registration at the Los Angeles federal building.

The Reverend Al Sharpton, an African American activist from New York, is a critic. "The way it's being handled is atrocious. I think the registration program itself raises the question of whether or not we're doing something based on race, based on nationality," he said.

More than 30 civil rights groups and immigrant organizations have asked President Bush to end the program, saying it targets people based on race, religion and national origin rather than intelligence information.

Francisco Arcaute of the Immigration and Naturalization Service defends the registration, which includes in its second phase the nationals of many Middle Eastern countries and Afghanistan. "We're just asking individuals from those countries that are on the list to register. I add that this is done in the interest of national security," he said. "We have selected these countries because those are countries where terrorism has taken place. We have concerns. Also, I think it is perfectly legitimate for the American public to want to know who is in their country and what is their purpose here."

Churches, civil rights groups and immigrant organizations sent monitors this time to keep an eye on the process.

Next week, nationals of Pakistan and Saudi Arabia who are in the United States temporarily must begin to register in the third phase of the program.