Sydney Airport is warning thick fog over the city is likely to impact flights today. 

The city woke to fog lying about 50 metres above ground, spanning from the city's south to north-western suburbs.

A spokesperson for Sydney Airport said the weather conditions will be monitored through the morning.

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"Fog has descended at the airport resulting in delays and cancellations across the network. We will continue to monitor the weather conditions as the morning progresses. 

"We advise passengers to check the status of their flight with their airline."

It has already impacted flights into Sydney, with two international passenger services diverted to Brisbane airport.

Three cargo flights have also been diverted to Brisbane.

The Bureau of Meteorology has issued a warning of treacherous conditions on the city's roads.

"Reduced visibility in fog will make road conditions dangerous during Wednesday in all suburbs," a spokesman said.

"Motorists are advised to take extreme care."

Entrepreneurial Australians may be lured abroad to New Zealand or the United States after the federal government overhauled the tax treatment for investments, business owners warn.

NZ finance minister Nicola Willis may have been tongue-in-cheek when she recently invited Aussies to hop across the ditch – where there is no comprehensive capital gains tax (CGT) – but business owners may be seriously considering the move.

Founders say scrapping the 50 per cent CGT discount, which will drastically reduce profits for some business owners who decide to sell, is the death knell for Australia's start-up culture.

EXCLUSIVE: Expat Annie decided to move back to the UK. She lasted just six months

Do you have a story? Contact reporter April Glover at

A crash between a bus and a train travelling at high speed in northern Belgium has killed four people, including two children, and injured five other children, officials say.

The injured children were hospitalised in a serious condition, said Lisa De Wilde, spokeswoman for the East Flanders public prosecutor's office.

The collision happened at a level crossing during the morning rush hour on Tuesday (Tuesday afternoon AEST) near the town of Buggenhout, more than 30 kilometres north-west of the capital, Brussels.

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The minibus driver and an escort were killed along with two children, 12 and 15, De Wilde said at a news conference.

She said that the cause of the crash hadn't been established. Investigators were questioning witnesses and checking security camera footage.

"What we do know is that the barrier was closed and the red light was on," she said.

An Associated Press reporter at the scene said the badly damaged bus lay toppled on its side, its front section crushed flat.

Forensic experts in protective white suits and wearing gloves were taking photos of the scene. A forensics tent was erected nearby. The train was relatively unscathed.

The train was estimated to be travelling at about 120km/h as it approached the crossing and had "no time to brake", said Frédéric Sacré, a spokesman for Belgian rail operator Infrabel.

"The impact was extremely violent," Sacré told RTBF public broadcaster.

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Federal Police spokesperson An Berger said that the bus driver appeared to have ploughed through the train barrier.

Infrabel said that the crossing was working correctly. A security camera there showed that the bus, which had nine people aboard, was still moving when the train hit it.

It's believed that 100 passengers were aboard the train and that none of them were hurt. Rail traffic in the area was halted and bus services provided for travellers. Local officials stood for a minute's silence after the news conference.

Children played basketball and rode bicycles at a school not far from the scene in this bucolic town.

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In a social media post, Interior Minister Bernard Quintin expressed "great sadness" over "the tragic accident in Buggenhout, where a school bus was struck by a train".

"My thoughts go out to the victims and their loved ones," he said.

He told a jury his ex-partner’s allegations were ‘lies’, ‘bulls***’ and ‘utter crap’.