Qatar’s foreign minister has dismissed reports of threats of military action by Saudi Arabia over Doha’s plans to acquire the Russian-made S-400 air defence system, saying Qatar’s decision to buy weapons is a “sovereign” one.

The threats, Mohammed bin Abdulrahman Al Thani said on Monday, violates “international law and all the international norms”.

“The purchase of any military equipment is a sovereign decision that no country has anything to do with,” Al Thani told Al Jazeera.

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In a letter addressed to French President Emmanuel Macron, Saudi King Salman expressed his “profound concern” with talks under way between Moscow and Doha for the sale of the advanced anti-aircraft weapon system, French daily Le Monde reported on Friday.

The Saudi monarch, who asked that France increase its pressure on Qatar, said he was worried about the consequences of Doha’s acquisition of the mobile surface-to-air missile system, which he said threatened Saudi security interests.

“[In such a situation], the Kingdom would be ready to take all the necessary measures to eliminate this defence system, including military action,” King Salman was quoted as saying in the letter.

“This letter has no legal basis to justify any action,” Al Thani said in an interview with Al Jazeera.

“It’s unfortunate that they see this as destabilisation because Qatar does not represent a threat to Saudi,” he said.

‘Violates GCC charter’

The foreign minister of the gas-rich nation also said that the threats “violate GCC charter”, which says that member countries should not attack each other.

The purchase of any military equipment is a sovereign decision that no country has anything to do with Mohammed bin Abdulrahman Al Thani, Qatar foreign minister

Al Thani said Qatar is currently seeking formal confirmation of the reported threat from the French government.

Tuesday marks one year since Saudi Arabia, Bahrain, the United Arab Emirates and Egypt severed diplomatic and trade ties with Qatar, sparking the biggest diplomatic crisis in the Gulf in years.

Accusing Doha of supporting “terrorists” and being too close to Saudi Arabia’s regional rival Iran, Riyadh said it acted to “protect its national security from the dangers of terrorism and extremism”.

Land and maritime borders with the Gulf country were shut, air links suspended and Qatari citizens expelled.

Qatar has repeatedly rejected the “baseless” accusations levelled against it, viewing the campaign as an attempt to impose custodianship over the nation.

If Saudi’s threats are confirmed, Al Thani noted his country will “respond legally … as we are not violating international law”.

“Qatar is going to treat this the same way we have treated the illegal blockade, we are going to seek all the international forums to make sure that this behaviour is not repeated,” he said.

When asked if Qatar plans to go ahead with the military purchase, Al Thani said “all options are open” at this time.

“We’re going to take all the necessary actions to defend our country,” he said, noting that the reported letter does not pose a “serious” threat at this time.

The decision to buy military equipment requires “subjective evaluation by the military”, the Qatari minister said.

“It’s not a decision that we will be taking in light of a threat.”