U.S. President Donald Trump on Monday threatened again to raise tariffs on goods from India over its Russian oil purchases, while New Delhi called his attack "unjustified" and vowed to protect its economic interests.

In a social media post, Trump wrote, "India is not only buying massive amounts of Russian Oil, they are then, for much of the Oil purchased, selling it on the Open Market for big profits."

"I will be substantially raising the Tariff paid by India to the USA," he added.

A spokesperson for India's foreign ministry said in response that India will "take all necessary measures to safeguard its national interests and economic security."

"The targeting of India is unjustified and unreasonable," the spokesperson added.

Trump has said that from Friday he will impose new sanctions on Russia as well as on countries that buy its energy exports, unless Moscow takes steps to end the Ukraine crisis. Russian President Vladimir Putin has shown no public sign of altering his stance despite the deadline.

Over the weekend, two Indian government sources reportedly told Reuters that India will keep purchasing oil from Russia despite Trump's threats.

India has faced pressure from the West to distance itself from Moscow since Russia-Ukraine conflict broke out in early 2022. New Delhi has resisted, citing its longstanding ties with Russia and economic needs.

Trump had already in July announced 25 percent tariffs on Indian imports, and U.S. officials have cited a range of geopolitical issues standing in the way of a U.S.-India trade accord.

India is the biggest buyer of seaborne crude from Russia, importing about 1.75 million barrels per day of Russian oil from January to June this year, according to a Reuters report.

India began importing oil from Russia because traditional supplies were diverted to Europe after the outbreak of the Russia-Ukraine conflict, the Indian spokesperson said, calling it a "necessity compelled by global market situation."

The spokesperson also noted the West's, particularly the European Union's, bilateral trade with Russia: "It is revealing that the very nations criticizing India are themselves indulging in trade with Russia."

(With input from Reuters)