No group, not even Syria, can get a grip on Lebanon

''Six cease-fires fail to halt widespread shelling of city,'' read the front-page headline on a west Beirut newspaper Wednesday. Below it was a picture of two children dashing across an abandoned street to avoid snipers' bullets.

On an east Beirut paper, banner headlines described the situation as ''mad'' and ''barbaric.''

On both sides of Lebanon's capital, Christians and Muslims seemed to agree that a much-heralded disengagement plan, announced Monday night, was falling apart even before it could be put into action. The plan to halt fighting was endorsed by the government and militias as the first constructive step since last month's peace talks in Lausanne, Switzerland.

The plan was important because a stable truce would in theory allow the warlords to get on with the more crucial issue of political reforms, without the distractions of fighting.

There are still some limited hopes for the plan, tied to President Amin Gemayel's anticipated summit in Syria with President Hafez Assad in the next few days. Mr. Gemayel is expected to appeal to Damascus to use its leverage on Lebanon's Muslims and Druzes to get them to adhere to a cease-fire and to moderate their political demands.

As the instability increases, two trends have emerged, according to Lebanese and Western diplomats:

* Although Mr. Assad reportedly wants a rapid resolution of the Lebanese crisis, Syria is experiencing the same problems the US did during its 17-month effort to end the crisis. One key diplomat said Wednesday that ''Damascus so far has not shown it has the ability, influence, or acumen to control Lebanon.''

There is some concern in Lebanon that Syrian internal hassles, centered on Assad's health problems and apparent jockeying for position among possible successors, have weakened Syria's ability to cope with Lebanon.

* Mr. Gemayel, a Christian, appears unable to control Christian elements. Western military sources who divide their time between east and west Beirut claim these elements have been responsible for most provocations over the past two months. They say Christian ''Lebanese Forces'' militiamen and pro-Christian Phalange elements in the Lebanese Army have been linked to as many as 85 percent of the violations, although independent confirmation is impossible.

But at the same time, the two main non-Christian militias - the Shiite Muslim ''Amal'' and the Druze Progressive Socialist Party - have shown little ability or will to control smaller groups in west Beirut that have been tied to sabotaging the cease-fires. These groups, which are largely Shiite, include the Lebanese Communist Party and the Organization for Communist Action in Lebanon.

Although the details of the disengagement plan have not been publicized, it reportedly calls for minor pullbacks - from 10 to 700 yards - by the militias along the ''green line'' that divides Christian east and Muslim west Beirut, and in the strategic nearby town of Souk al Gharb. Some 2,000 gendarmes and retired Army officers would patrol the buffer zones.

One of the most dangerous aspects of the current fighting is the random nature of targets. Panic broke out on Hamra Street, west Beirut's main shopping district, when shells and rockets landed there during one of many incidents. There are no major strategic positions on Hamra.

The targeting of east Beirut is similar, although government installations have been hit. Just hours after the disengagement plan was announced, the Lebanese Forces warned they would retaliate immediately if the east was hit, rather than wait for mediators to try to calm the situation.

The majority of victims are civilians. The list of refugees grows daily.

The fragile military situation is matched politically by the Cabinet led by Prime Minister Shafik Wazzan. The Cabinet, which resigned in February but agreed to stay on during the Lausanne talks, now wants out. Mr. Wazzan has begun to pressure Mr. Gemayel to form a new cabinet. But it is highly unlikely that a formula for power-sharing among the minority ruling Christians and the majority Muslims can be reached at this stage. Some fear that Lebanon may witness a repeat of the period under former President Suleiman Franjieh, when the country was without a government for eight months.