DUBAI, Dec 5 (Reuters) - Stock markets in the Gulf fell in early trade on Monday as investors took profits on gains in the past few weeks after the mood in global markets darkened because of the 'no' vote in Italy's referendum on constitutional reform.

The euro EUR= has dropped to a 20-month low and investors are exiting riskier assets after Italian Prime Minister Matteo Renzi said he would resign following the referendum defeat, which could destabilise the banking system of Europe's third largest economy.

Riyadh's main index .TASI lost 1.0 percent after 70 minutes of trade with all but one of 14 listed petrochemical shares slipping. Blue chip producer Yanbu National Petrochemical 2290.SE fell 1.5 percent.

Most petrochemical shares have rebounded strongly over the last several weeks and are trading close to what analysts estimate to be their fair values.

Similarly, the Saudi banking sector sub-index .TBFSI fell 0.9 percent. All blue-chip lenders pulled back with Al Rajhi Bank 1120.SE slipping 1.2 percent.

Dubai's index .DFMGI edged down 0.1 percent, dragged lower by profit-taking in some large caps which had gained strongly on the previous day. Emaar Properties EMAR.DU fell 0.4 percent.

But some smaller shares were resilient, with builder Drake & Scull DSI.DU adding 2.5 percent in heavy trade. Deyaar Development DEYR.DU climbed 3.9 percent after the company said it was offering a guaranteed 14 percent return to investors in one of its Dubai luxury residential projects.

In Abu Dhabi, the index .ADI fell 0.1 percent in volatile trade, dragged down for a second day by telecommunications giant Etisalat ETEL.AD , which lost 1.1 percent. On Sunday, Etisalat pulled back 3.5 percent.

(Reporting by Celine Aswad; Editing by Andrew Torchia; Editing by Andrew Heavens) ((celine.aswad@thomsonreuters.com)(+9715 6224 7653))