Turkish President Tayyip Erdogan has told Turks to sell their gold and US dollars to support the country's currency, which has plunged after US President Donald Trump escalated a feud with his NATO ally by doubling tariffs on Turkish metal imports.

The Turkish lira has long been falling on worries about Mr Erdogan's influence over monetary policy and worsening relations with the United States.

Yesterday the currency dropped as much as 18% at one point, the biggest one-day fall since a 2001 financial crisis in Turkey.

Reverberations spread through global financial markets, with European stock markets especially hit as investors took fright over banks' exposure to Turkey. US stocks were also rattled.

The lira has lost more than 40% this year. It hit a record low after Mr Trump announced he had authorised higher tariffs on imports from Turkey, imposing duties of 20% on aluminium and 50% on steel.

The lira, Mr Trump noted on Twitter, "slides rapidly downward against our very strong Dollar!"

"Our relations with Turkey are not good at this time!" he wrote.

An important emerging market, Turkey borders Iran, Iraq and Syria and has been mostly pro-Western for decades. Financial upheaval there risks further destabilising an already volatile region.

Without naming countries, Mr Erdogan said supporters of a failed military coup two years ago, which the Turkish authorities say was organised by a US-based Muslim cleric, were attacking Turkey in new ways since his re-election two months ago.

This afternoon, Mr Erdogan said the US has turned its back, saying such treatment has upset them.

"This treatment by America of its strategic partner has annoyed us, it has upset us," he said.

The new duties on Turkey are double the level that Mr Trump imposed in March on steel and aluminium imports from a range of countries. The White House said he had authorised them under a section of US trade law that allows for tariffs on national security grounds.

Turkey's trade ministry said the tariffs were against World Trade Organisation rules.