The Australian sharemarket kicked off December on a weak note as investors rotated out of defensive stocks and banks, with US futures also pointing to a weak session on Wall Street.

The S&P/ASX 200 Index fell 48.9 points, or 0.6 per cent, to 8565.2 in a disrupted session after about 80 companies were placed into lengthy trading halts following an outage that prevented the ASX from publishing market-sensitive announcements for three hours.

US futures were also pointing to a fall of more than half a per cent for the US sharemarket, while bitcoin slid as much as 6 per cent to below $US86,000 in early Asia trading, further pointing to a risk-off session overnight.

Bell Potter’s Richard Coppleson said there was no real reason for the fall in the US futures, other than both the S&P 500 and the Nasdaq rallying more than 3 per cent last week.

“Maybe some just thought it’d gone too hard in a thin market and sold them today,” Coppleson wrote in a report to clients. “Bitcoin dropping back to US$85,876 may have also weighed.”

Losses on the ASX were led by healthcare, with CSL falling 1.4 per cent to $183.64 and Chemist Warehouse operator Sigma down 1.4 per cent to $2.84.

Consumer staples also weakened, with Metcash tumbling 9.2 per cent to $3.36 after reporting just a 0.1 per cent rise in revenue to $8.48 billion for the half-year to October 31, missing expectation for 1 per cent growth.

Financials also dragged the index lower as AUB slumped 17.8 per cent to $30.63 after ending takeover talks with suitors EQT and CVC

The major banks also weighed with Commonwealth Bank falling 0.6 per cent to $151.64, National Australia Bank 0.6 per cent to $39.85, Westpac dropped 0.9 per cent to $37.26, and ANZ 1.3 per cent to $34.20.

The ASX fell 2.8 per cent to $56.58 after its announcements platform suffered the lengthy outage.

There was a modest rotation into commodities that helped lift the materials sector. Woodside gained 0.9 per cent to $25.16 as global oil prices rose more than 1 per cent after OPEC+ reaffirmed its planned pause in supply increases.

And a 1 per cent increase in iron ore supported the major miners, with BHP rallying 1 per cent to $42.08, Fortescue rising 0.8 per cent to $21.58 and Rio Tinto 0.4 per cent to $132.76.

Stocks in focus

Treasury Wine fell 0.7 per cent to $5.78 as it booked a significant non-cash impairment on its US operations, writing off $687.4 million in goodwill.

Healius rose 2.6 per cent to $1 after securing a five-year, $60 million contract to provide private pathology services to the Australian Defence Force.

Energy One dropped 7.3 per cent to $16.38 after director Ian Ferrier said he would sell about 315,000 shares, worth roughly $5.4 million, to fund a property purchase.

APA slipped 0.4 per cent to $9.22 after signing a joint development agreement with CS Energy for a gas-fired project in Queensland that is scheduled to begin operating in 2028.

And Pro Medicus declined 1.6 per cent to $262.18 as it secured a new $25 million, seven-year deal with US health network BayCare, expanding its footprint in the Tampa Bay and central Florida regions.