A car bomb apparently targeted at an office of the Christian Phalangist Party killed nine persons and wounded two dozen today in a suburb of east Beirut. It was the sixth attack in two weeks against the wing of the Christian community that supports President Amin Gemayel.

The blast shattered the ground floor of a shopping complex in New Jdeide, wrecking boutiques, gutting a dozen ships and setting an apartment afire. The Phalange office across the street, apparently the target of the bomb, was not damaged.

On Jan. 21, a powerful car bomb also apparently aimed at a Phalange Party office killed 28 and wounded 132. That bomb came six days after bloody fighting between two Christian factions forced strongman Elie Hobeika out of the leadership of the Lebanese Forces, the combined Christian militia.

Friday, a bombing injured two women in Sin Fil, a Christian neighborhood of east Beirut. Yesterday two bombings at two other Phalangist Party offices wounded four persons. An Armenian suburb of east Beirut was rocked by three more explosions yesterday, but there were no casualties.

Although fears of a Syrian-backed military offensive against the Christian heartland of Lebanon have subsided for now, the bombings have alarmed residents and focused attention on a drive to oust Gemayel.

The Maronite Christian president's strong opposition to a Syrian-mediated peace plan led to the battles between the Christian Lebanese Forces and Phalange Party fighters loyal to Gemayel that forced Syrian ally Hobeika into exile Jan. 15. Hobeika has now joined a Syrian-backed effort to revive the contested accord and unseat Gemayel.

Hobeika has been meeting in Damascus with Nabih Berri, leader of the Lebanese Shiite Moslem Amal militia, as part of efforts to organize an anti-Gemayel campaign. Hobeika, Berri and Druze leader Walid Jumblatt, who said he objected to some of its provisions, signed the agreement last December.

Berri, whose Shiite Moslem community stands to gain the most from the draft agreement, told reporters today upon his return from Damascus that he had a plan to press ahead with it. "Political action is under way to implement the agreement," he said. "I am for cutting short the term of the president, which is constitutional."

Meanwhile, in Moslem west Beirut, an second unknown group said in a statement delivered to a foreign news agency that it had abducted South Korean diplomat Do Chea Sung, 43, and threatened to execute him unless its unspecified demands were met.

The group, which called itself the Fighting Revolutionary Cells, said: "We call on the South Korean government to meet all the demands that we will put forward; otherwise he will be liquidated." The warning was accompanied by a photograph of the diplomat holding up the current issue of Time magazine.

Yesterday, another unknown group, the Green Brigades, claimed it had kidnaped the South Korean and asked for $10 million for his release.

Do, the first Far Eastern diplomat to be kidnaped here, was seized by gunmen while he was driving to work Friday.