* Wheat turns lower, corn and soybeans also retreat

* Grain traders monitoring Russia news after aborted mutiny

* Weekend rains in Midwest aid crops, but drought persists

CHICAGO, June 26 (Reuters) - Chicago wheat futures declined on Monday in a technical and profit-taking retreat after concerns about political stability in major exporter Russia had lifted prices earlier to four-month highs.

Corn and soybeans also pared early gains, with corn turning mostly lower as milder temperatures and crop-boosting rains in parts of the U.S. Midwest over the weekend tempered some worries about drought-reduced yields.

Grains markets had opened the week on a strong note as an aborted mutiny in Russia by Wagner Group mercenaries over the weekend stoked concerns that grain flows from the breadbasket region could be disrupted.

Chicago Board of Trade September wheat was down 11-1/2 cents at $7.35 a bushel at 12:36 p.m. CDT (1736 GMT) after peaking at $7.70-1/4 in early trading, the highest since Feb. 23. Several wheat contracts briefly rose above their 200-day moving averages, but failed to hold gains above the key technical level.

"More uncertainty caused some short covering in wheat, but that's really simmered down since the open ... We've reached a key technical objective in the Chicago wheat so we'll see where it goes from here," said Ted Seifried, chief market strategist with the Zaner Group.

Sluggish U.S. export demand and rising supplies from the ongoing winter wheat harvest, which analysts expect is 29% complete, also hung over wheat futures.

Dry Midwest weather and declining crop conditions kept a floor under corn and soybean markets, although weekend rains in some northern crop areas lessened concerns about the drought.

Analysts polled by Reuters expect the U.S. Department of Agriculture to lower its corn and soy crop ratings by 3 points in a weekly report later on Monday.

CBOT new-crop December corn was down 5-1/4 cents at $5.82-3/4 a bushel, while November soybeans were 6 cents higher at $13.16 a bushel.

(Additional reporting by Michael Hogan in Hamburg and Naveen Thukral in Singapore, editing by Emelia Sithole-Matarise, Vinay Dwivedi and Christina Fincher)