The Indian rupee weakened past 87 to the U.S. dollar for the first time ever on Monday in the wake of a slump in Asian currencies and equities after U.S. President Donald Trump's tariff threats became a reality.

Asian currencies and equities also slumped as a result of the tariffs, which have sparked fears of a trade war

The rupee breached the key 87 per dollar mark, touching an intra-day low of 86.30 per dollar, prompting the Reserve Bank of India (RBI) to step in, which helped the Indian unit cut some losses to close at 87.91/$, down 0.7 per cent from its previous close.

The Indian rupee fell to a record low on Monday after U.S. President Donald Trump slapped tariffs on imports from the country's three biggest trade partners, stoking fears of a trade war that rattled global financial markets.

The dollar index was up 0.3% at 109.8, while Asian currencies weakened, with the offshore Chinese yuan down 0.5% at 7.35 per US dollar.