CARACAS, Venezuela — A visit to Venezuela by two military airplanes from Russia, which landed in broad daylight at the international airport in Caracas, has set off alarms that the Kremlin might be acting more brazenly to protect President Nicolás Maduro from the uprising against him.

Russian and Venezuelan officials have not disputed the arrival of the airplanes, which were first seen at the airport on Saturday. Such flights ordinarily would be sent to a protected military air base beyond the sight of the public.

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The planes brought supplies and technical advisers to Caracas, Venezuela’s capital, according to a Russian state news agency and a Russian diplomat. The visit was related to military cooperation contracts signed years ago between Russia and Venezuela, said the news agency, Ria Novosti, suggesting it was routine.

A Russian diplomat in Caracas, who spoke on condition of anonymity because the diplomat was not authorized to speak to the media, confirmed the Ria Novosti account and said there was nothing unusual.