DUBAI, April 25 (Reuters) - Two Qatari blue chip shares weighed on the local index in early trade on Tuesday after reporting a disappointing set of quarterly earnings, while Dubai was dragged lower by telecommunications operator Du.

Qatari Islamic lender Masraf Al Rayan lost 0.5 percent after reporting a 6.5 percent year-on-year fall in its first-quarter net profit to 510 million Qatar riyals ($140.1 million) and below the average of three analysts' estimate of 517.1 million riyals.

Commodities shipper Qatar Navigation was down 1.0 percent after it made a net profit of 236 million Qatar riyals ($64.81 million) in the three months to March 31, down 33 percent from the prior year period and below the 369.2 million riyals analysts at QNB Financial Services had estimated.

Doha's index was down 0.3 percent.

Dubai's index was down 0.6 percent as shares of Emirates Integrated Telecommunications (Du) lost 3.0 percent after reporting a net profit of 364.9 million dirhams ($99.35 million) in the three months to March 31, down 24 percent from the prior year period.

Analysts at SICO Bahrain forecasted the telecommunication provider to make a net profit of 447.33 million dirhams and EFG Hermes estimated 474.02 million dirhams.

Shares of developer DAMAC Properties, which has not yet reported earnings, slumped 9.8 percent as they went ex-dividend on Tuesday.

Shuaa Capital, however, bucked the trend to add 1.9 percent after it swung to a first quarter net profit of 24.8 million dirhams, from a net loss of 28.5 million dirhams in the prior year period.

In Abu Dhabi, the index added 0.2 percent as Abu Dhabi Islamic Bank climbed 2.5 percent after it reported a 20 percent year-on-year growth in first quarter net profit to 577.5 million dirhams.

Saudi Arabia's index slipped 0.3 percent in the first half an hour of trade with the main drag from the petrochemical sector as Brent crude futures were trading near a four-week low around $51.70 a barrel. Heavyweight Saudi Basic Industries fell 0.5 percent.

Most petrochemical makers have not yet reported earnings as the regulator granted companies an additional 15 days to publish financials since they are converting to IFRS from the current local standard.

But shares of apparel retailer and mall operator Fawaz Alhokair extended on yesterday's 10 percent gain, to add 4.4 percent. On Sunday, the retailer reported a huge jump in net profit despite a small drop in sales.

(Reporting by Celine Aswad; Editing by Angus MacSwan) ((celine.aswad@thomsonreuters.com)(+9715 62247653)(Reuters Messaging: celine.aswad.thomsonreuters.com@reuters.net))