President Yitzhak Navon of Israel, pledging his nation's commitment to "friendship, brotherhood and cooperation," began a five-day visit to Egypt today, the first by an Israeli chief of state to any Arab country.

Despite tension over lack of progress in the Palestinian autonomy negotiations, President Anwar Sadat gave Navon an elaborate state welcome that eclipsed receptions given Prime Minister Menachem Begin on any of his five visits to Egypt in nearly three years.

This was seen as a sign that Sadat wants to impress on the Israeli people Egyptian willingness for friendly relations despite the autonomy dispute, which many Egyptian officials impute directly to Begin. Sadat frequently has hinted at a strategy of appealing to Israeli public opinion as a way of bringing pressure on Begin or whatever Israeli government follows his for concessions in the negotiations.

But Egyptian officials denied that the warm welcome for Navon was meant as a snub to Begin. It merely reflected the progress in Egyptian-Israeli relations, they said.

The remaining disagreement over Palestinian autonomy was underlined by a powerful bomb that exploded on the main road leading out of Jerusalem to Tel Aviv, wounding 15 soldiers according to a police count. Two other bombs also went off during the day, one near Tel Aviv and the other in the occupied West Bank.

The Palestine Liberation Organization in Beirut claimed responsibility for the blasts, saying they were in retaliation for Israeli raids on guerrilla targets in southern Lebanon.

The Israeli president, who will have three sessions with Sadat during the five-day visit to Egypt, wields little power. Under the Israeli system, political decision-making is the prerogative of Begin and his Cabinet ministers.

"I am carrying with me to the Egyptian people words of peace and truth," Navon said before departing Tel Aviv, "words of our steadfast dedication to friendship, brotherhood and cooperation."

Navon said he did not expect the visit to produce great achievements, "but as far as Egypt's relationship to us is dependent on understanding our feelings and needs, possibly there will be certain advantage. Days will tell."

Sadat, leading a long line of government officials, shook hands with Navon when he disembarked from his Israeli Air Force jet. The two stood at attention as a 21-gun salute was fired and the Egyptian and Israeli anthems were played. The two men then reviewed an hour guard and received flowers from children.

From the airport, Sadat and Navon drove through streets of Cairo bedecked with Egyptian and Israeli banners. Few Egyptians lined the route of their motorcade.

After a banquet in Navon's honor at the Abdin Palace this evening, Sadat and Navon will hold business talks Monday morning. Officials said the talks will be of a general nature and are expected to focus relations, which Israelis have complained is going too slowly because of the autonomy problems. i