Gunmen attacked a crowd of worshipers outside Rome's main synagogue with grenades and submachine guns today, killing a 2-year-old boy and wounding 34 other persons, several of them seriously.

The terrorists -- apparently four men, at least two described by witnesses as "dark-skinned" -- escaped after the attack, the latest of several against Jews in European cities in recent months.

Angry Jews, milling about on the blood-spattered sidewalk outside the synagogue, blamed the Palestine Liberation Organization and accused Pope John Paul II and Italian President Sandro Pertini of creating the climate for the attack by meeting last month with PLO leader Yasser Arafat. Police tonight broke up a march by hundreds, many of them Jews, toward the PLO office in Rome.

The pope condemned the attack as "a criminal action" and a "manifestation of blind hate and violence," and Pertini in a telegram to Rabbi Elio Toaff called the attack "an act of unqualifiable barbarism." A PLO spokesman here also condemned it.

Four anonymous calls to three Italian newspapers and the state television claimed that the attack had been carried out by a group called the PLO-Red Brigades, combining the Palestinian organization with Italy's chief terrorist group. But police said they were not taking the calls seriously.

The attack was the most severe against Jews in Italy since the end of World War II and the ninth directed against European synagogues during the past three years. An attack on a Jewish restaurant in Paris in August killed six persons and injured 22.

Today's attack began when the terrorists walked up to the main gate of the massive temple, which stands on the banks of the Tiber River, shortly before noon. After throwing three or four hand grenades, they fired into the crowd and then fled, either on foot or in a car, leaving behind them dozens of bleeding and fallen people.

By nightfall, about 30 spent 9-mm cartridges of the type manufactured in Eastern Europe were found, said police, who despite roadblocks throughout the city had found no sign of the gunmen.

Stefano Tache, 2, died in a hospital shortly after the attack. His 4-year-old brother Marco, who had shrapnel fragments in the chest and brain, also was reported near death and his mother and father were among those hospitalized.

Many children were among the victims because this morning's religious service included a ceremony for the young. Religious Jews were celebrating Simhas Torah, the ninth and final day of the harvest festival known as Sukkot that falls shortly after the Jewish New Year.

Dr. Marco Zarfati, an Israeli who was in the temple at the time and was one of the first to aid the wounded, said: "The scene outside the synagogue was terrible. Seven or eight people were lying on the ground, some in serious condition."

The street was covered with splintered glass from the windows of parked cars. There was a large pool of blood on the doorstep of a nearby apartment house, where several wounded persons had taken refuge.

The Jewish community of Rome is one of the oldest in Europe, predating Christianity. With 16,000 active members, it is Italy's largest.

About 10 hours after the attack, two bombs -- one at the unoccupied Syrian Embassy and another at the Islamic Center -- exploded nearby, but there were no reports of injuries, The Associated Press reported. No group claimed responsibility.

After the attack at the synagogue, hundreds of angry Jews from the surrounding area, still known today as "the ghetto," gathered outside the temple chanting slogans against the pope and Pertini for their recent meetings in Rome with Arafat.

At one point, brief fistfights broke out with a few Arabs who shouted anti-Jewish slogans. Several reporters, including at least three Americans, were manhandled by irate Jewish Italians who said they believed today's attack was instigated by allegedly anti-Israeli press coverage here at the time of the massacre of Palestinians in Lebanon.

The only kind words were for Premier Giovanni Spadolini, who did not see Arafat during the Palestinian leader's first official visit here in mid-September. Spadolini promised the crowd at the synagogue that security would be strengthened.

The PLO representative in Rome, Nemer Hammad, sharply condemned the attack, calling it "an aberrant manfestation of anti-Semitism against our Jewish brothers, guilty only of being Jews."

A statement by the Israeli Embassy sharply condemned "all those responsible for creating anti-Israeli feeling in the weeks following the massacres in Lebanon."