DUBAI, April 30 (Reuters) - Petrochemical shares helped lift the Saudi Arabian bourse in early trade on Sunday after strong first-quarter earnings in the sector. Neighbouring stock markets were mostly lower.

Saudi Kayan Petrochemical surged 7.9 percent after it swung to a net profit of 265.5 million riyals ($70.8 million) from a loss of 195 million riyals in the prior-year period. Analysts at NCB Capital had expected a profit of 121 million riyals.

"This is the highest net income since inception. We believe the variance is due to higher-than-expected operating rates and gross margin," NCB Capital said.

The positive mood spilled into shares of other producers, most of which have not yet posted quarterly earnings. Saudi Arabia Fertilizers (SAFCO) rose 2.2 percent after it reported net income of 423 million riyals, at the high end of forecasts; the consensus estimate was 406 million riyals.

The Saudi stock index was up 0.6 percent after half an hour of trade.

Dubai's index was flat, staying near a 4-1/2 month low, as 12 shares declined and 11 rose. Second- and third-tier shares, which are often traded by local day-traders, were the top movers, with GFH Financial Group jumping 4.8 percent but builder Arabtec was down 0.8 percent.

In Abu Dhabi, the index edged up 0.3 percent with support from blue chips; telecommunications operator Etisalat rose 1.2 percent and real estate developer Aldar Properties added 0.5 percent.

Qatar's largest petrochemical maker, Industries Qatar, rose 0.7 percent after news that one of its units, QAPCO, had signed an agreement with state-owned Qatar Petroleum to supply the low-density polyethylene producer with additional ethane gas.

Other Qatari shares sagged, however, dragging the index 0.2 percent lower. Vodafone Qatar was the worst performer, down 1.4 percent.

(Reporting by Celine Aswad; Editing by Andrew Torchia and David Evans) ((celine.aswad@thomsonreuters.com)(+9715 62247653)(Reuters Messaging: celine.aswad.thomsonreuters.com@reuters.net))