A Lebanese-born Palestinian was charged today with throwing a hand grenade into a crowded sidewalk cafe last night along the fashionable Via Veneto. The blast injured 40 persons, including eight Americans, according to figures supplied by the State Department.

The attack occurred at the outdoor tables of the Cafe de Paris, which became famous 25 years ago in Federico Fellini's film "La Dolce Vita."

Identifying the cafe attacker as Ahmed Hossein Abu Sereya, Rome Police Chief Marcello Monarca told a news conference today: "For us, he is the man."

But eyewitness accounts of the attack differed from the police account and left unclear whether the grenade that exploded was tossed by someone on foot or from a passing car or motorcycle. Witnesses also said they heard gunshots behind the cafe before the grenade blast.

Monarca said that police had spotted Sereya running from the scene immediately after a grenade -- one of two thrown -- exploded on the sidewalk near cafe tables that were crowded with tourists sipping late-night coffee and drinks. Sereya was found to have a plane ticket from Damascus, Syria.

A second grenade, which did not explode, was set off by police explosives experts early this morning after the usually crowded Via Veneto, where the U.S. Embassy is located, had been sealed off.

Monarca said that Sereya, carrying a false Moroccan passport, was captured by the police after a half-mile chase through darkened streets.

Sereya, who talked to an Arabic-speaking Italian journalist, denied he was responsible for the attack that occurred in an area normally crowded with tourists from all over the world.

"I am a Palestinian, I fight for my people, but I did not do what I am being accused of," the Italian news agency ANSA reported the 27-year-old Sereya as telling the Arabic-speaking journalist.

The police explanation of seeing Sereya on foot hurrying away from the scene did not tally with some eyewitness accounts.

"I was sitting at a table with my wife shortly after 11 p.m. when I heard three shots," said Manuel Villaverde, 52, a Spanish engineer who lives in Buenos Aires. "I told my wife to get on the ground and I threw myself on top of her. There was an explosion, and I don't remember too much after that."

Villaverde, in an interview from his bedside at Rome's San Giacomo Hospital today, said his wife, who received a cut on the face in the blast, remembers a dark car speeding by the restaurant shortly before shots and an explosion. Villaverde was hit by grenade fragments and had wounds from his hips to his toes.

"My feeling is that the gunshots were fired to make people get up from the tables before the grenade went off," Villaverde said. "But coming from Argentina and knowing about those things, I didn't stand up but hit the ground."

Villaverde's story of hearing shots before the blast was corroborated by his hospital roommate, Derrick Hamlin, a 43-year-old engineer from London, who said he, too, heard shots before diving to the ground as the explosion occurred.

Police did not account for these differing versions or the possibility that Sereya may have been an Arab walking in the area who panicked when the explosion occurred.

No group has claimed responsibility for the attack, and police admitted that they were still not sure how many people had been involved in carrying it out.

"We still don't know if there were one, two or three people involved," Monarca said. "We have several ideas as to the motive and are examining them, but for the moment I cannot say anything else.

"We don't think it was a deliberate attack against Americans or any other group," the police chief said. "There wasn't one big group of tourists but lots of small groups of different nationalities who were there by chance."

Monarca said that a search of Sereya's hotel room near the Via Veneto had uncovered a plane ticket that showed he had flown from Damascus to Vienna, then made his way to Italy overland. He had an unused portion of the round-trip ticket to return to Syria from Vienna.

Only one of the injured, the cafe's cook who was serving tables when the blast occurred, was injured seriously.

Most were either treated at emergency hospitals and released last night or released during the day. Only a handful of wounded remained in the hospital tonight, including Villavarde and Hamlin.