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TSX ends down 1.6% at 24,759.15

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Posts biggest decline since March 4

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Technology sector falls 3%

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Aya Gold & Silver ( AYASF ) tumbles 15.8%

(Updates at market close)

By Fergal Smith

March 28 (Reuters) - Canada's main stock index fell on Friday by the most in three weeks as U.S. data and an expanding trade war raised fears of a global economic slowdown.

Toronto Stock Exchange's S&P/TSX composite index ended down 401.91 points, or 1.6%, at 24,759.15, its lowest closing level since March 18 and its biggest decline since March 4. For the week, the index was down 0.8%.

Major U.S. benchmark, the S&P 500, posted an even steeper decline.

"When the president of the United States tries to shut down the global economy it can be problematic for stock markets," said Matt Skipp, president of SW8 Asset Management. "How can any business leader make an impactful decision, whether it's purchasing for their businesses, when the government changes its mind every day."

U.S. consumer spending rebounded less than expected in February while a measure of underlying prices increased by the most in 13 months, stoking fears the economy was facing a period of tepid growth and high inflation amid an escalation in trade tensions.

Canadian GDP rose 0.4% in January but a preliminary estimate showed activity flatlining in February. U.S. President Donald Trump and Prime Minister Mark Carney had a conversation that both men described as productive, although the Canadian leader said Ottawa would be imposing retaliatory tariffs next week as promised.

On Wednesday, Trump announced a 25% tax on imported vehicles. Autos are Canada's second-largest export.

The technology sector was the biggest decliner, falling 3%, with e-commerce company Shopify Inc ( SHOP ) ending 5.7% lower.

The materials group, which includes metal mining shares, fell 1.7%. It was weighed down by a 15.8% drop in the shares of Aya Gold & Silver Inc ( AYASF ) after the company reported quarterly results. Consumer discretionary fell 2.2%, with auto parts suppliers adding to their recent declines and shares of Restaurant Brand International losing 6.1%.

Industrials were down 2.2% as railroad shares declined and heavily weighted financials ended 1.6% lower. (Reporting by Fergal Smith in Toronto and Ragini Mathur and Sanchayaita Roy in Bengaluru; Editing by Sahal Muhammed and Deepa Babington)