A maximum-security "screen" will surround Cuban Premier Fidel Castro this afternoon as soon as his train pulls into Back Bay Station, and an estimated 300 to 500 policemen will guard him during his speech tonight at Dillon Field House. Police reports indicate that the crowd may reach 10,000.

Rumors of plots to kill the revolutionary leader account for the extensive police precautions. One such rumor--that a seven-man group was planning to assassinate Castro--was investigated yesterday. Police found five of the men working peacefully in Philadelphia, and another located in Las Vegas, Nevada. All of the men denied any plot.

Concern for Castro's safety has also caused the Law School Forum, sponsors of tonight's speech, to take unusual security measures. The Forum has refused to sell tickets to non-members of the University, or to anyone at the gate.

As many as 200 police will guard the ten-foot fence and entrances which surround the seating area at the Field House, to keep anyone without a ticket from entering. In addition, three cordons of police will surround the Field House itself, and others will circulate in the crowd.

(Associated Press Bulletin, New York) Police last night seized a man carrying a makeshift bomb behind the band shell from which Cuban Premier Fidel Castro was addressing a rally of 35,000 in Central Park. More than 1,000 policemen guarded Castro throughout his appearance.

Officials to Meet Castro

The Premier will arrive at Back Bay Station at 3:30 this afternoon with his party of 71, and will be met by J. Hampden Robb '21, University Marshal, Edward Petullo, assistant Dean of the Faculty of Arts and Sciences, Law Forum officers, and local Cubans.

A caravan of four limousines, two buses and two baggage trucks, will transport most of the party to the Statler Hilton, where an entire floor is reserved for the night. At 6:25 the party will leave the hotel for a reception and dinner at the Faculty Club.

Police to Guard Faculty Club

Both Quincy and Prescott Sts. will be completely blocked off for traffic while the Premier is at the Faculty Club, and the club will be heavily guarded. The entire dinner party of about 150 Cubans and Faculty members will leave the club with Castro at 8:25 for the speech.

At the Field House, Robert A. Sidenberg 2L, President of the Forum, will introduce Dean Bundy, who will in turn present Castro. After the speech and question period, Castro is scheduled to attend a reception in his hotel at 11:25.