AS Sabahans began voting yesterday in a state election, the Malaysian Prime Minister, Datuk Seri Dr Mahathir Mohamad, raised the spectre of Malaysia becoming another Bosnia if the ruling party in Sabah was returned to power. Dr Mahathir said that during the election campaign, the Parti Bersatu Sabah (PBS), which split with the National Front federal coalition in 1990, had aroused hatred towards the federal Government as well as racial, religious and parochial sentiments which could undermine unity. ''Does the PBS want to turn this country into a Bosnia-Herzegovina or Northern Ireland or Kashmir?'' Dr Mahathir asked. He rejected as totally untrue what he described as PBS claims that the federal Government wanted to colonise Sabah and that under a National Front government Christians would be oppressed. Dr Mahathir urged the people of Sabah to reject the ''divisive and hate politics'' of the PBS. His statement was seen as a last-ditch effort to turn the tide running against the federal Government's favoured candidates. Between 20,000 and 30,000 people in remote areas of the interior of Sabah, mainly from the Kadazan-Dusun and Murut indigenous communities, cast their ballots on the first day of voting and the rest of the state's 598,000 eligible voters go to the polls today. To reach booths yesterday, many voters travelled long distances by river craft or on foot through jungle trails. It took election officers several days of trekking through thick tropical vegetation, accompanied by porters carrying ballot boxes and armed guards, to reach Sabahans in some of the more isolated constituencies. Even before Dr Mahathir's strong statement, the National Front mounted a vigorous campaign to oust the PBS. But all the indications here are that despite promises of new spending made by Kuala Lumpur and appeals for votes by Dr Mahathir and other federalgovernment leaders, PBS rule will continue. Dr Mahathir's statement capped a campaigned marked increasingly by dirty tricks and divisive tactics as the election approached. In a state where Christians and Muslims live amicably together, a number of candidates played on underlying religious fears. A cartoon on a National Front leaflet showed the Chief Minister of Sabah, Datuk Joseph Pairin Kitingan, a Christian Kadazan, dressed as the Pope and carried by supporters who were treading on opposition supporters. Responding to rumours that a victory for the mainly Muslim National Front candidates would result in Christians being forced to give up their religion, the Deputy Prime Minister, Datuk Seri Anwar Ibrahim, said if they won they were not going to ''go around circumcising people''. In a reflection of the bitterness the election campaign has engendered, Mr Anwar ruled out co-operation with the PBS if it was returned to power. ''I want to say in no uncertain terms that we are not prepared to co-operate with the PBS based on its track record, the personalities involved and the policies,'' he said.