DUBAI, April 3 (Reuters) - Kuwait's equity index underperformed while United Arab Emirates climbed ahead in an otherwise quiet region in thin early trade on Monday.

Kuwait's index , which has been one the best performing stock markets in the world since the start of the year, fell 0.9 percent.

Most of the usually heavily traded stocks fell, with the largest warehouse manager in the Gulf, Agility Public Warehousing,and Kuwait Food Co each down 1.6 percent.

Hospital manager Al Mowasat Healthcar slumped 6.8 percents as its shares went ex-dividend.

Qatar's index was down 0.5 percent with number of declining shares outnumbering number of advancing ones nine to seven. Islamic lender Masraf Al Rayan was the main laggard, dropping 3.9 percent.

In Riyadh, the index edged down 0.2 percent in very thin trade. Some 62 shares declined and 45 were up after 25 minutes of trade.

Domestic-focused shares were some of the main underperformers, with electronics retailer United Electronics Company down 1.2 percent and healthcare provider Taiba Holding falling 1.4 percent.

Meanwhile, United Arab Emirates bourses outperformed. Dubai's index was up 0.5 percent with the previous session's most heavily traded shares - Union Properties - up 2.5 percent in above average trade.

Other small and mid-sized shares often traded by day traders were also outperforming.

Abu Dhabi's index rose 0.4 percent as Sunday's top performer Abu Dhabi National Energy jumped 7.8 percent. On Sunday, shares of the oil explorer and power supplier had jumped their 15 percent daily limit in heavy trade.

A Dubai-based portfolio manager said that the spike in volume amid a still low turnover - relative to other traded shares - suggested only a few players had pushed share prices significantly higher.

The largest real estate developer Aldar Properties was up 0.9 percent.

(Reporting by Celine Aswad; Editing by Saeed Azhar and Tom Heneghan) ((celine.aswad@thomsonreuters.com)(+9715 62247653)(Reuters Messaging: celine.aswad.thomsonreuters.com@reuters.net))