KARACHI, PAKISTAN, MAY 31 -- Unidentified gunmen poured automatic-weapons fire into a crowded bus here today, killing at least 30 people and wounding 30 others as the latest outbreak of bloodshed in this ethnically turbulent city continued into a third week.

At least eight other people were slain by gunfire around Karachi today, bringing the death toll in ethnic clashes in the teeming port and surrounding Sind province since May 15 to more than 300. No one claimed responsibility for the bus attack.

The violence stems from deep hatred between native Sindis and the Mohajirs, descendants of Moslems who immigrated to Pakistan from Hindu India during the 1947 partition of the subcontinent. Sindis accuse the better-educated Mohajirs of taking the best jobs and most valuable land.

Police blame the latest clashes on a militant faction of the Mohajir Qaumi Movement, a small political party representing the Moslem Indian immigrants. The party is demanding recognition as Pakistan's fifth nationality, along with Pathans, Punjabis, Baluchis and Sindis.

The bloodshed has forced Prime Minister Benazir Bhutto to postpone a four-day trip to Qatar, Iraq, Kuwait and Bahrain, during which she was to seek support in Pakistan's dispute with India over the future of Indian-ruled Kashmir.

Moslem nationalists in Kashmir are trying to break away from Indian control, and the New Delhi government has accused Pakistan of fomenting civil disorder there. Pakistan denies the charge.

Bhutto has rejected demands that she counter the violence by dismissing Sind's provincial government -- headed by her Pakistan People's Party -- and bringing Sind under control of central authorities in Islamabad. Instead, she has called out the army to help restore order.

Today, soldiers patrolled the largely deserted streets of Karachi, which is the capital of Sind and the country's financial and industrial hub.