British authorities today directly implicated the Syrian government for the first time in the attempt three months ago to plant concealed explosives aboard an Israeli airliner leaving here for Tel Aviv with nearly 400 aboard.

A 31-year-old Palestinian, charged with trying to place the bomb aboard the El Al flight last April, was "acting on instructions, apparently from the Syrian government," a British prosecutor alleged today.

The prosecution said that Nezar Hindawi had admitted responsibility for the unsuccessful bombing attempt. It said that after planting the bomb in the suitcase of his unsuspecting girlfriend who was due to board the flight, Hindawi had followed instructions to go to the Syrian Embassy in London, where he met with Ambassador Loutof Haydar.

Today's proceedings, a preliminary hearing for the prosecution to demonstrate that sufficient grounds exist to bring the case to trial, marked the first time British authorities have accused Syria publicly of complicity in the April 15 incident.

Damascus has been linked circumstantially to Hindawi, a Jordanian citizen who entered Britain last February using a false Syrian passport, ever since his arrest the day after the bombing attempt. But government officials until now have avoided any direct reference to possible Syrian involvement in planning or placing the bomb.

On May 11, Britain expelled three Syrian diplomats after their government refused to waive diplomatic immunity to allow them to be questioned in the case. In late May, however, Prime Minister Margaret Thatcher said Britain "at the moment has no such evidence against Syria of state-sponsored terrorism of anything like the kind that obtains in the case of Libya."

Syria, and Ambassador Haydar, repeatedly have denied any involvement in the bombing attempt. Damascus is said to be conducting its own investigation of the case, and some Syrian officials reportedly have suggested that their government is being "framed," perhaps by Israel or an anti-Syrian terrorist organization with Hindawi's help. They have suggested that the plot included the bomb's discovery at the airport, before it went off.

Lawyers acting for Hindawi during today's hearing did not question the prosecution's account of his alleged confession. Instead, their examination of official police witnesses appeared to concentrate on circumstances surrounding his interrogation and widespread publicity following his arrest.

It remained unclear during today's hearing whether the prosecution would offer any evidence of a Syrian link other than Hindawi's own testimony in a full trial. Under British law, the media here are not allowed to report any of today's proceedings, and government officials later declined to respond to questions about the case.

In its opening statement, the prosecution said without explanation that it was dropping one of two initial charges brought against Hindawi -- that of "conspiring with others" to murder the 358 passengers, plus crew members, aboard the plane. In addition to a remaining original charge of trying to "cause an explosion aboard an aircraft," police have added charges of unlawful possession of a gun and ammunition, which were found with Hindawi at the time of his arrest.

Today's presentation by the prosecution was somewhat sketchy but it added a number of details to previously reported accounts. When Hindawi arrived here last February, it was alleged today, he was accompanied by two men also carrying Syrian passports.

In early April, he asked his girlfriend, Anne Marion Murphy, an Irish national, to marry him on learning she was pregnant with his child. He bought her the April 15 ticket to Tel Aviv as a wedding gift and dropped her off at London's Heathrow Airport that morning with a suitcase. He said he would take a later flight.

At the El Al departure gate, an Israeli security official determined the suitcase had a false bottom and contained plastic explosives and a timing device. Murphy was released two days after the incident because police said that there was insufficient evidence to show that she had committed a criminal offense.

The prosecution said Hindawi was to fly via Syrian Arab airlines to Damascus but followed an alternative plan and allegedly was directed to Syrian Ambassador Haydar, who arranged for him to spend the night.

The next morning, however, Hindawi turned up alone at a hotel run by a Jordanian who with Hindawi's brother convinced Hindawi to turn himself over to the police, the prosecutors said.