Russian spy satellites mapped out the UK-US military base on the Chagos Islands after Iran launched missiles towards it.
Volodymyr Zelensky was told of the Russians "helping" Iran in an intelligence briefing on Saturday outlining Moscow's satellite operations.
He said Russia was deploying its surveillance capabilities "in the interests of Iran", photographing American and British installations across the Middle East.
"On March 24, they imaged the US-UK joint military facility on Diego Garcia, located in the Chagos archipelago in the Indian Ocean," Mr Zelensky said.
That was four days after Tehran attempted to attack Diego Garcia.
One missile was shot down by a US warship, while the other failed in flight.
The British Ministry of Defence is still yet to confirm exactly when the attempted strike took place.
Russia took pictures of the Diego Garcia base from space just four days after Iran launched missiles towards it
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And the MoD has previously assessed it is "highly likely" that Moscow shared intelligence with Tehran before hostilities began last month.
That cooperation now appears to be intensifying.
Mr Zelensky revealed that Russian satellites had photographed civilian and military sites throughout the Gulf region to pass on to Tehran.
"On March 25, they took pictures of the Prince Sultan air base in Saudi Arabia. The Shaybah oil and gas field in Saudi Arabia, Incirlik air base in Turkey and Al Udeid air base in Qatar were all imaged on March 26," he said.
Iran launched its attack on Prince Sultan base just one day later, on March 27.
Al Udeid, which houses US Air Force and RAF personnel alongside other foreign forces, has also come under fire during the conflict.
Al Udeid, which houses US Air Force and RAF personnel alongside other foreign forces, has been targeted
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Russian satellites also took photos of the Shaybah oil and gas field in Saudi Arabia before it was struck
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The Incirlik air base on Nato ally Turkey's soil has come under fire too, though the country has refused to draw in the alliance so far.
The assault on Prince Sultan base proved devastating, wounding 12 American service members.
An E-3 Sentry radar aircraft was destroyed in the strike, with refuelling planes also sustaining damage.
Analysts believe Russian intelligence may have been behind the attack's precision.
Mr Zelensky also revealed Russia's three-stage satellite plans which can give away whether an attack is underway.
A £370million E-3 Sentry radar aircraft was destroyed in the strike
"We know that if they make images once, they are preparing.
"If they make images a second time, it's like a simulation.
"The third time, it means that in one or two days, they will attack," he told NBC News.
He said he was "100 per cent" confident of the intelligence link.
Moscow has denied any accusations of sharing information with Tehran - though it has admitted it provides the Iranian regime with "certain types of military equipment".
Volodymyr Zelensky outlined Russia's three-stage satellite plans
| GETTYEuropean intelligence services now believe Moscow is preparing to go further.
They assess that Russia is readying supplies of attack drones for Iran, having spent years testing and refining the weapons during its war against Ukraine.
The supply of drones would be the first instance of Russia directly handing the Islamic Republic lethal weaponry in the war.
And it could set up direct Russian attacks on American forces, with thousands of US troops amassing in the Middle East as of Monday morning.