Shiite Moslems have emerged from three years of chaos and fighting around their poor villages near the border with Israel as an increasingly mobilized political and military force competing for power in Lebanon.

The growth in Shiite self-awareness and political organization here flows in part from inspiration generated throughout the Moslem world by Ayatollah Ruhollah Khomeini and his Shiite-led revolution in Iran. It also reflects a particular outrage at the suffering of Shiite villagers in southern Lebanon's battlegrounds and a new realization of the strength of numbers in Lebanon's sectarian power sharing.

The growth of the Lebanese Shiite population, which with 900,000 members forms the country's largest religious group, has combined with determination to have a louder voice in government to raise the prospect of increased Moslem influence in a country traditionally controlled by Christians and oriented toward Europe.

Shiites here differ from Sunni Moslems less on theology than economic status. The difference in doctrine stems chiefly from an ancient quarrel over the authentic lineage among descendants of the Prophet Mohammed, who founded Islam. But in Lebanon, Sunni Moslems traditionally look down on Shiites, who form a class of poor farmers and laborers while Sunnis in general shared more broadly in Lebanon's pre-civil-war wealth.

The Shiite movement here has a powerful symbol in the Imam Musa Sadr, who disappeared without a trace 14 months ago while visiting Libyan leader Muammar Qaddafi in Tripoli.

Sadr's photograph, showing him in a neat graying bread and Shiite turban, is on posters pasted throughout Beirut's Moslem quarters. "Oh Arabs, Where is the imam?" says the legend on one. Shiite leaders still regularly invoke his name with reverence in conversation.

Officially, they maintain hope he will return to continue the fight for Lebanese Shiites. His deputy and the country's acting Shiite leader, Sheik Mohammed Mehdi Shamseddin, reproached an interviewer who referred to Sadr as "the late" imam.

In fact, most Shiites here believe Sadr was murdered by Qaddafi's secret police because of a political quarrel. When the Libyan leader tried to drive to Lebanon from Syria last summer, he was forced to turn back because of demonstrations and threats on his life in Beirut.

Sadr was raised in Iran, where his father taught at the holy city of Qom, and he spoke Arabic with a Persian accent. But he was fiercely Lebanese and it was largely he who gave new impetus to Shiite demands for more attention from the Lebanese government.

First he formed a Higher Shiite Council to give the community political leadership and press its case with the Christians and Sunni Moslems who traditionally have held the controls of government. Then he formed the Movement of the Deprived to underpin the council with an organized mass of followers.

During the Lebanese civil war he helped form Amal, or hope, a militia designed to protect Shiites in the Beirut and Sidon slums and refugee tents where many fled to escape shelling in their southern border villages. The militia has since obtained such weapons as mortars and grenade launchers and has taken its place among the nearly 20 armed groups that help make Lebanon look like a painting by Hieronymus Bosch.

Amal gunmen in the Beirut quarter of Shiah clashed recently with units from the Palestine Liberation Army serving with the mostly Syrian Arab peace keeping force stationed in Beirut since November 1976.

The clash left about 15 dead and wounded, underscoring the Shiites' increased power and dramatizing the disillusionment of many Shiites with Palestinians.

Thousands of Shiites have been forced to flee their villages in the south because of clashes there between Palestinians and Israelis or Israeli-backed Christian forces. This upheaval has generated broad resentment in the community. It is growing despite traditional Shiite support for the Palestinian cause and continuing declarations of such support from Shiite leaders.

"There is no contradiction between support of the Palestinian cause and refusal to accept the status quo in the south," said Kamel Asaad, speaker of the Lebanese Parliament and the highest Shiite government official. "The Shiites are not against the Palestinians. The are against the status quoo in the south."

Asaad said in an interview that the solution lies in a halt to Palestinian armed operations there and restoration of Lebanese sovereignty through Lebanese Army forces. Independent observers hold out little hope for such a solution, however, as long as the Palestinians insist on military independence and Israel continues to buffer its border through "Free Lebanon," its protectorate under rebel Lebanese Army Maj. Saad Haddad.

In the meantime, Lebanon's Shiites are looking to Iran for increased assistance to deal with Shiite refugees and organize the community into a stronger political force. Iranian money is said to help support Amal and finance its weapons. Sheik Shamseddin said, however, that Iranian aid so far has been so small as to be negligible.

But he added: "It is to be expected that if it was a matter of life and death, the Shiites would receive special attention from the Iranian revolution."

The differences between Moslems in the sectarian atmosphere of Lebanon run deep. A Sunni woman who works in a government ministry has to sneak visits with her Shiite boyfriend because her parents refuse to let them get engaged or go out openly together. A Shiite maid who was refused a handout at the Saudi Embassy recently complained that the Sunnis had taken all the money.

Sunni concern has risen recently because of the Shiites' high birth rate, particularly in farm villages of the south where families of a dozen children are common. Sunnis, traditionally more urban and economically advanced, follow the Christian example more frequently and limit families to several children.

"We are the only ones in Lebanon who have so many children," laughed Abu Ali, a Shiite father of 11 from the southern town of Nabatiyeh.