Special to The New York Times.

HAVANA, April 18--The youthful followers of Fidel Castro have gone into hiding throughout Cuba.  They are striving desperately to reorganize their rebellion against President Fulgencio Batista and to escape the army's relentless killings.

In Oriente Province in particular youths are fleeing form population centers to join the rebels in the mountains.  The rebels lack of arms and ammunition is serious, but rebel sources here say some arms are being received by air in the Sierra Maestra stronghold of Senor Castro.

Fierce fighting is going on in Oriente, but censorship has blacked out detailed reports of it.  A decree issued yesterday provided sever penalties for violation of the censorship and for citizens who criticize or oppose the Government.

A Cuban Army communiqué said thirteen youthful revolutionists had surrendered to the armed forces at Corralillo in Las Villas Province.  The communiqué said these rebels had delivered to the authorities three shotguns, a rifle, two revolvers and some ammunition.

Despite the constant alert of the armed forces and the hundreds of police cars twenty-four-hour patrol, Havana is relatively peaceful.  Cubans, long inured to military rule, went about their business as usual today.  The streets were full of shoppers.  Traffic was heavy.

Weekly lottery tickets are being sold in Havana at 20 cents instead of 25 and 30 cents.  The reason for this apparently is that Havana is flooded with unsold lottery tickets from the interior.  The villagers have refused to buy tickets.  Observers say this is an indication of the disturbed condition in the interior.

The National Bank of Cuba bas withdrawn its order of April 14 that reserve requirements of banks be raised May 1 from 30 to 40 per cent on demand deposits.  This measure was designed to stimulate investment in Government securities.