Wearing the traditional scarlet papal mourning cape, pope Paul VI yesterday led Italian government and political figures and official representatives of about 100 foreign nations in a solemn funeral mass for terrorist-slain Christian Democratic leader Aldo Moro.

In the huge square outside Rome's Basilica of Saint John's in Lateran, thousands of labor union and party workers and simle citizens listened in silence to the ceremony broadcast over loudspeakers.

Dozens of red Communist and white Christian Democratic flags were massed together in the square in a growingly familiar sight since the first protest demonstrations the day Moro was kidnapped March 16.

Inside, the official mourners included Communist Party leader Enrico Berlinguer, the architect with Moro of the "historic compromise" between Italian Catholics and Communists that the Red Brigades, who murdered Moro, have been working to undo.

The pope's participation in a funeral service for a layman was an unprecedented gesture to the late Christian Democratic leader. The 80-year-old pontiff had made a personal plea "on bended-knee" to the Red Brigades to release Moro unharmed. The two men had known each other for decades, from when the pope was a university chaplain and Moro was a Catholic student union leader.

"Lord hear us," intoned the pope yesterday, "you did not heed our plea for the safety of Aldo Moro, this good, gentle, wise and innocent friend, but you Lord have not abandoned his immortal spirit."

In the front pews of the cathedral of Rome were Moro's sister, Maria Rosaria, wearing a black mantilla, and his brother, Carlo. Their presence was apparently a conciliatory gesture by the Moro family, which has bitterly accused the Christian Democrats of abandoning Moro because they refused to negotiate for his release.

Moro's widow, Eleonora, and their four adult children nevetheless stood by their decision not to attend the ceremony, which was conducted as a funeral mass in every detail except for the absence of Moro's coffin. The Moro family whisked it away from the morgue on Wednesday and buried it immediately in a private funeral from which all public figures were excluded.

Yesterday's ceremony flew directly in the face of the family's statement the day of Moro's killing that, in accordance with the wishes he expressed in his letters from captivity, there be "no national mourning, no state funeral, no medals in his memory."

As if to stress that they intend to press their campaign against the Italian state and establishment, leftist terrorists carried out three sabotage operations overnight. No one was injured in the attacks.

One of the attacks, against a repair and wasehouse facility of the Honeywell computer company in Milan, was the second this week against American interests in Italy.

Five guerrillas overpowered the night watchman and two cleaning men, spread gasoline around the building and set it ablaze. Company officials estimated damage at more than $1 million.

Responsibility for the arson was claimed by the same group that said earlier in the week that it was responsible for the legshooting in Milan of the Italian branch manager of New York's Chemical Bank.

In other action Friday night, terrorists blew up a showroom for Alfa Romeo cars in Milan and cut power lines from an electric power station leading to an Alfa Romeo plant near the city. The automaker has been a particular target of terrorists who object to a labor contract requiring overtime work on Saturdays.

The chief U.S. representative at the funeral mass, Health, Education and Welfare Secretary Joseph Califano Jr., issued a statement here calling the Moro killing "an affront not only to Italy but to civilzation."

Praising Moro, Califano said, "The qualities he personified - moderation, counciliation, steadfast devotion to a democratic Italy - survive. Those qualities, I believe, will prevail over the arrogance and cowardice of his attackers."

Pope Paul read a special prayer that he had written this morning in memory of his friend, who was 61.

"We have come together in our cathedral of Rome to pray and bear witness," the pope read, "in a world of hate and blood, that God's love may conquer everything. We invoke the Holy Spirit so that the violence of hatred may be overcome by the force of forgiveness and love."

The pope's voice was frail, as it has been in several recent appearances, reflecting his advancing years and his recent illness. It was his first visit outside the Vatican since a bout of influenza forced him to cancel most of his Eastertide observances.

The pope rode the two miles frothe Vatican in his black bulletproof limousine, waving to the crowds that lined his route. As part of the reinforced security all over the city, he was surrounded by nine armed motorcycle guards.

Hundreds of soldiers and police were stationed outside the basilica. All over the city, there were soldiers stationed in their smart gray battledress wearing navy blue berets and carrying machine guns.

Mass in the basilica was celebrated by the vicar of Rome, Cardinal Ugo Poletti. Moro's sister and brother were the first to advance to take communition.

At the end of the service, other Moro relatives and widows of two of the five bodyguards who were killed when Moro was kidnapped each advanced for a few private words with the Pope.

Another widely noted absentee from the services yesterday was Francesco Cossiga, who resigned this week as interior minister to accept personal responsibility for the failure of the police to rescue Moro. Cossiga went to the tomb of Moro this morning.

The ceremony was held in the sumptuous baroque basilica that is Rome's oldest church, largely rebuilt in the 17th century. It was sung by the choir of the Vatican's Sistine Chapel.

There were dozens of wreaths and simple bouquets at the spot where Moro's body was found in the back of a car parked in a side street in central Rome between Communist and Christian Democratic headquarters. The spot has been turned into an informal shrine with pictures of the dead man, votive candles and a large notebook under a makeshift canopy where visitors sign their names.

Strategically placed at the highest point on the shrine yesterday was a large floral arrangement with red ribbons instead of the traditional black ones inscribed from "The Communists of Rome."

Most of the bunches of flowers and handwritten, usually religious, messages from private citizens who signed their first names only or anonymously with such inscriptions as "a mother."

One of the handwritten signs read. "I often critized you, and you belong to another party, but I will always remember you as a loyal and honest man. A student."

Police said yesterday that they were hunting for a professional killer in connection with Moro's death, a former French Foreign legionnaire named Glustino de Vuono, 38. He escaped from an Italian prison last year.

But the authorities denied published reports that there had been written warnings beforehand by police and bodyguards that Moro needed additional protection because suspicious persons had been seen following his car.

The presence of Moro family representatives at the ceremony was seen more as a gesture toward the pope than as a sign of softening in their hostility to the Christian Democratic Party.

Despite the family's attitude, the party appears to have come out of the crisis surrounding the kidnaping of nearly two months duration with its image and prestige enhanced in the country.

By sticking to its refusal to negotiate with relatively little hesitation or backbiting, it gave an impression of unity and determination that had been missing. The previous impression of drift and factionalism was generally considered to be at least partially responsible for the party's succession of electoral defeats in recent years.

Giovanni Balloni, a vice secretary of the Christian Democratic Party who stood in the front row of the church yesterday with the party's other leaders said in an interview:

"The Moro family's position is a moral but not a political embarrassment for us. The family cannot monopolize a national figure like Aldo Moro. We respect the family, but Moro also belonged to his party and his country."

Political analysts generally expect that the Christian Democrats will benefit from a sympathy vote in local elections today and Monday. Eyes are particularly turned toward two fair-sized northern cities - Pavia (Pop. 88,000) and Novara (Pop. 102,000). They are respectively near terrorist-hit Milan and Turin.

The Communists went to great pains during the crisis to project an image of responsibility and fair play. This has undoubtedly strengthened the party's place as part of the governing majority in parliament.

Analysts think the party may nevertheless be hurt electorally because, for the man in the street the terrorists' constant stress on the word "Communist" in their communiques and in many of group names they use makes them kissing cousins to the regular Communist Party.

Apparently trying to head off such a backlash against his party. Communist chief Berlinguer said in a televised election campaign program this week, "We are all in the same boat now. As a Communist, I have been trained to expect that I might have to sacrifice my life some day."