In ceremonies spanning the heavily armed frontier between Egypt and Israel, the leaders of the two former enemy countries today proclaimed their borders open to visits by each other's citizens.

Flanked by Egyptian President Anwar Sadat and Secretary of State Cyrus Vance, Israel Prime Minister Menachem Begin stood in a rustic movie theater in El Arish - the Sinai Peninsula capital returned to Egyptian control Friday after 12 years of Israeli occupation - and announced:

"President Sadat and I proclaim that the borders of Israel and Egypt are open. Citizens of Egypt will be able to visit Israel; citizens of Israel will be able to visit Egypt."

For the present, the border opening appears more symbolic than real. Officials on both sides cautioned that details still must be worked out about who may visit and under what conditions. It is likely to be some time before any mass exchanges of people take place.

But, even as a symbol, the announcement was important. It resolved a dispute that had threatened to cloud implementation of the Egyptian-Israeli peace treaty and it set a tone of good will that dominated the festivities that began this morning in El Arish and then moved north across the border 60 miles to this Israeli city in the Negev Desert.

At the end, Begin and Sadat, accompanied by Vance, capped the day of speeches and toasts to friendship by boarding an Egyptian jetliner that flew the first part of a flight over a newly opened air corridor that will link Tel Aviv and Cairo.

Despite the upbeat tone, the day included discordant reminders that there is still a long way to go before the peace accord can be expanded into a comprehensive settlement between Israel and the Arab states.

The wide gap that remains was underscored by hard-line positions taken by the Israeli and Egyptian delegations when they met here Friday to begin negotiations on self-government for the 1.1 million Palestinians in the West Bank and Gaza. Despite the friendly atmosphere pervading the ceremonies today, echoes of those differences could be heard clearly.

Sadat was visibly angered at a welcoming speech in a flag-bedecked parking lot next to Beersheba's city hall by Israeli President Yitzhak Navon, who referred to the "sacrifices" being made by Israel in surrendering El Arish and evacuating the Sinai.

"It is no light matter when we withdraw from it, for we are giving substantial strategic depth . . . airfields it cost us much labor to build, a network of roads, buildings and stores, and avital source of oil," Navon said.

In responding, Sadat departed from his text and testily reminded Navon that the Sinai was always "Arab land" and that Israel was not giving up anything of its own.

He recalled that when he went to Jerusalem in November 1977 to initiate the peace process, he told the Israeli parliament, or Knesset, "that the land will not make security, Just as the land of Israel is sacred to its people, the land of others is sacred to them."

"I didn't come to the Knesset to ask you for my land. I came to tell you, let us start a new era of love instead of hatred. Let us not argue about who was right and who was wrong. Let us write a new chapter . . ."

His words were a pointed reference to Israel's reluctance to surrender its hold not only on the West Bank and Gaza Strip but also on such other conquered territory as East Jerusalem and the Golan Heights of Syria.

Sadat's peace with Israel has exposed Egypt to isolation and bitter criticism from other Arab countries, and the Egyptian leader is eager to extract territorial concessions from the Israelis to vindicate his course.

But after a 20-minute meeting with Navon following the speeches, Sadat apologized for what he said was a misunderstanding of the Israeli president's address, which was made in Arabic. Navon reportedly told the Egyptian president he did not mean to imply that Israel was giving away land it considered sovereign Israeli territory.

The dispute was further thrust into the background by the ceremonial events that began early this morning in El Arish. Sadat was waiting there at a stucco seaside villa - formerly the Israeli Water Authority headquarters, and before the 1967 war an Egyptian officers' club - to receive Vance, who represented the United States at the opening of the autonomy talks Friday, and a delegation of Israeli Cabinet ministers headed by Begin.

Amid hugs and handshakes, and small talk that included congratulations on Sadat's 30th wedding anniversary - he referred to it as "30 years of hard labor" - the tone was set. The two leaders and Vance conferred privately over lunch and then went to the El Arish meeting hall to a ceremony honoring Israeli and Egyptians wounded in the four wars fought by the two nations.

There, with Sadat looking on, Begin appeared to put an end to his dispute with Egypt's Deputy Foreign Minister Boutros Ghali and Prime Minister Mustafa Khalil by announcing the border opening. For several weeks, Ghali and Khalil have been contradicting Begin's statements about a swift process of normalization of relations - including border opening - saying that such steps would be taken after Israel's withdrawal from approximately half the Sinai Peninsula eight months from now.

Sadat, when asked about these misunderstanding, replied: "There is no misunderstanding. My ministry of foreign affairs was opposed to the idea, but I gave a promise to Begin. It was a matter of my ministry convicing me, or vice versa, and I convincedd them."

Begin also announced he will meet Sadat in Alexandria in the first week in July "to hold important talks. He added that Israeli Foreign Minister Moshe Dayan will go to Cairo next week to meet Khalil and Ghali and discuss the autonomy negotiations, which are scheduled to resume June 6 at Alexandria, Egypt.

In a unilateral gesture long expected, Begin also announced that Israel will release "a number of" Arab prisoners, but he stressed the amnesty would not impair Israel's security. Government sources said between 50 and 60 West Bank and Gaza Strip Palestinians held on suspicion of sub-version would be released.

Israeli officials said other methods of accelerating the normalization were agreed upon, but that the two leaders decided to withhold announcements on them until their meeting.

Also, Israeli Interior Minister Yosef Burg and Khalil discussed the autonomy negotiations and reached some unspecified agreements, officials said.

Begin is understood to have mentioned to Sadat the plight of settlers from the Neot Sinai settlement, two miles from El Arish, who will be unable to cultivate vegetable fields just inside the new border. The settlers had to be removed forcibly by Israeli soldiers just before El Arish reverted to Egyptian control.

However, Sadat is understood to have flatly rejected a proposal to allow the settlers access to the fields, and Begin dropped the matter.

Following the Beersheba city hall ceremonies, Begin, Sadat and Vance went to the Ben-Gurion University of the Negev, where the Egyptian president returned to the theme of territorial acquisition, saying: "Events of the recent past have shattered all concepts of security based on territorial expansion."

However, his and Begin's speeches were conciliatroy in tone, and several thousands of students who crowded the campus plaza warmly greeted the Egyptian leader. CAPTION: Picture, Secretary of State Vance, President Sadat and Prime Minister Begin enjoy a laugh at El Arish meeting. UPI; Map, no caption, The Washington Post