Wounded Cuban seamen arriving in Las Palmas, Canary Islands, today said they had been strafed by Moroccan fighter planes off the coast of the Western Sahara. The men were rescued by Spanish naval vessels after being attacked by aircraft Saturday.

The Cuban consul at Las Palmas said in a telephone interview that one of the injured men, who was in serious condition, had been strafed while in the water. He said two aircraft had attacked two Cuban tankers attached to the Cuban fishing fleet when they were 15 to 20 miles off the coast of the Moroccan-administered Western Sahara. The captain of one vessel was killed.

Asked who was responsible for the attack, Consul Jesus Fernandez Ponce said: "Who do you think has got fighter planes in that area? The men I've talked to say they were Moroccans."

Morocco broke off diplomatic relations with Cuba in Arpil in protest at the recognition by the Havana government of the Algerian-backed Polisario Front fighting for control of the Western Sahara. The Polisario Front has been waging a guerrilla war in the Western Sahara, formerly a Spanish colony, ever since Madrid ceded the territory to Morocco and Mauritania in November 1975.

The Rabat government has frequently accused Cuba of involvement in the Polisario Front movement, but reporters visiting the guerrilla camps in the Tindouf area in Algeria have seen no evidence of Cuban participation.

In Washington, a State Department official said Cuban medical units have been helping Polisario guerrillas at Tindouf. While there have been many allegations by the Moroccans, the official said, no firm evidence of Cuban combat involvement in the Saharan war has emerged.

(A report issued last week by Rep. Clement Zablocki (D-Wis.), who visited the area in April, said that Cuban and East German advisers and technicians "reportedly" were involved in training Polisario guerrillas.

According to the State Department, the Polisario attacked and sank a Spanish vessel off the Western Saharan coast a couple of weeks ago and has taken Portuguese sailors prisoner.

The Spanish Navy destroyer Churruca docked at Las Palmas early today with the dead body of Manuel Ventura, the captain of the Cuban fuel supply tanker Moroboro, who was killed in the aircraft attack. Also aboard the destroyer were the Moroboro's chief engineer Marciso Scull and first officer Jesus Medina, both seriously injured by burns and by the strafing.

The consul said Medina had jumped overboard in the attack and had been strafed while in the water as the aircraft attacked the vessels over a period of 45 minutes. A third injured seaman who arrived at Las Palmas was Jesus Quintero, the first officer of the second supply vessel Guillermo Pico. The consul said that the Moroboro and the Guillermo Pico were limping back to Las Palmas and were expected there late tonight.

According to the Cuban consul, who sid he spoke to the survivors, the two vessels were first circled by a light aircraft, and then the fighter planes appeared. A Spanish Navy statement said both ships had been attacked by unidentified aircraft and that an inquiry had been opened. There was no immediate reaction from Moroccan authorities.

Earlier this year a Spanish Navy vessel was strafed by Moroccan aircraft off the Western Sahara. Although an official protest was lodged, the matter was largely hushed up in the press here. There were no injuries in the attack.