HAVANA (AP) _ Hundreds of Cubans crowded post offices in the nation's capital on Monday, the first day to mail in applications for a lottery for U.S. visas.

Several dozen people also gathered outside the U.S. Interests Section in Havana hoping to turn in their applications in person. But police officers who blocked off residential streets around the mission reminded them that applications had to be sent through the mail.

The Cuban government explained the application rules earlier this month in the Communist daily Granma in an attempt to prevent crowding at post offices and around the U.S. mission.

However, Cubans waiting outside the U.S. mission said they feared that their applications would either be lost in the mail or seized by government officials. None would give their names for fear of government reprisals, including the seizure of their lottery application.

Cuban government officials in the past have rejected such fears as unfounded, saying that they agreed to the lotteries as a way of periodically easing demand by those who want to emigrate.

The visa lotteries were set up in 1994 by the U.S. and Cuban governments to end the ``boat people'' crisis, in which hundreds of thousands of Cubans set off for the United States on rickety rafts.

The United States agreed to give out at least 20,000 visas a year and to return any Cubans intercepted on the high seas. The boat exodus diminished significantly after the decision.

The lottery, the third of its kind, was announced earlier this month in Washington and runs through July 15. Winners, chosen by chance, are granted an interview with U.S. consular officers.

Applicants must answer questions about their education, work experience and relatives in the United States.

In the last lottery, in 1996, more than 436,000 applications were received. About 6,000 people were selected and allowed to immigrate with their immediate families.

During the the first lottery, in 1994, 190,000 people applied.