A series of bombings in the past week and rioting that left two persons dead today have escalated tensions between Moslems and Christians in the Malaysian state of Sabah and saddled the government of Prime Minister Mahathir Mohammed with a potentially serious new problem.

The tension in the state, located on the northern tip of Borneo island, has grown out of a local political dispute pitting the state government, run by a predominantly Christian political party, against a Malay Moslem party that claims a share of power.

As the dispute boiled over last week, violence erupted, apparently aimed at destabilizing the state government of Chief Minister Joseph Pairin Kitingan. In the past week, 26 bombings in the state capital, Kota Kinabalu, and two coastal logging towns have left at least three persons dead and seven injured, according to news reports.

The most extensive violence broke out today when police battled up to 2,000 Moslem marchers who rioted in the streets of Kota Kinabalu. Police declared a 12-hour dusk-to-dawn curfew in the state, the only one of 13 in Malaysia not controlled by Moslem parties.

Police Chief Ahmad Maulana Babjee told reporters in Kota Kinabalu that two persons were killed in the rioting: a Filipino Moslem who participated in the march and a 14-year-old boy who was run down by a car. Police said the rioters burned 29 cars and 30 shops, causing $2.5 million damage. They said 20 persons were arrested and hinted that up to 500 militant Moslems would be removed from a state mosque.

It was not immediately clear how the Filipino died. Witnesses reportedly heard gunshots, but there was no confirmation that police had opened fire. The police used tear gas and chased the marchers, some of whom were armed with iron bars, clubs and rocks.

The tension began building after an election last April in which Pairin's newly formed Bersatu Sabah party captured the state government with strong backing from the mostly Christian Kadazan ethnic group, the state's largest ethnic community. The United Sabah National Organization, a predominantly Moslem party, charged that Pairin had reneged on a coalition agreement, and tried to have its leader, Mustapha Harun, installed as chief minister.

Further wrangling led Pairin to dissolve the state assembly last month and call for new elections. Supporters of Mustapha responded with demonstrations, charging that Pairin's government was undermining Moslem rights.

The federal government under Prime Minister Mahathir has refused so far to intervene in the matter or declare a state of emergency. The issue was discussed at a Cabinet meeting today, but no details were released. Parliament rejected a motion to debate the matter.

Nevertheless, the issue clearly represents a new problem for Mahathir, who has had to contend in recent weeks with the resignation of his deputy, Musa Hitam, amid a public squabble and the publication of a report on the country's biggest financial scandal.