Speaking at a briefing for journalists in Jerusalem, Nikolai Patrushev also said evidence presented by the US alleging Tehran was behind attacks on oil tankers in the Gulf of Oman was of poor quality and unprofessional.
Mr Patrushev spoke to reporters after a three-way meeting with his Russian and Israeli counterparts in Jerusalem. He said Iran - an ally of Russia - had not briefed Moscow about the incident, but that the Russian Defense Ministry had concluded the drone entered Iranian airspace.
He said: "We have not seen any proof otherwise."
Mr Patrushev’s comments came after the US imposed new sanctions targeting Iran’s supreme leader and other senior officials, which US president Donald Trump said was a “proportionate response to Iran’s increasingly provocative actions”.
The US government claims one of those actions was the “unprovoked” shooting down of a US navy RQ-4A Global Hawk in international airspace over the Strait of Hormuz.
Iran said the drone, with a wingspan larger than a Boeing 737 and costing more than over $100m (£79m), had violated its territorial airspace – a claim now supported by Moscow.
Either way, it marked the first time Iran had struck the US military, which released a set of coordinates it claimed the drone was shot down at.
The US has also blamed Iran for attacks on two oil tankers earlier this month near the Strait of Hormuz, though US officials have so far provided publicly only shaky evidence for the claim, which Iran denies.
US disarmament ambassador Robert Wood said Mr Trump was leaving a path open to diplomacy, but that Iran would be making a mistake if it interprets restraint for weakness.
Mr Trump had last week ordered reprisal air strikes over the downed drone, but called them off at the last minute when he was told of the likely resulting loss of life.
On Tuesday, Iran’s foreign ministry said the sanctions on figures including the Ayatollah Ali Khamenei would mean the permanent closure of diplomatic channels between Tehran and Washington.
Iranian president Hassan Rouhani later called the penalties “idiotic” and said the White House was “afflicted by mental retardation”.
Tensions have been mounting in the Gulf since Mr Trump withdrew the US from a 2015 multilateral deal in which Iran agreed to limit its nuclear programme in return for the lifting of crippling economic sanctions.
On Tuesday, the UK, Germany and France issued a joint statement calling for “de-escalation and dialogue” amid “grave concern” about increased tensions in the region.
They also reiterated their commitment to the 2015 nuclear deal, and urged “all sides to do the same”.
“It is in everyone’s interest to show restraint and avoid any actions that would undermine this vital pillar of the non-proliferation regime and of our collective security,” the statement said.
Additional reporting by agencies
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