* Australian food, vitamin stocks fall on China import rules
* Companies, analysts seek clarity over new rules
* Stockmarket star Blackmores falls as much as 18.6 pct
* New rules raise questions over China-Australia FTA (Adds dateline)
By Byron Kaye and Adam Jourdan
SYDNEY/SHANGHAI, April 12 (Reuters) - New restrictions on online imports in China sent shares of Australian food and health goods companies tumbling on Tuesday as investors sought clarity on rules that could affect one of the stronger parts of the country's export sector.
Analysts say the heavy selling in the segment has been driven by prevailing confusion over a raft of new measures authorities in mainland China announced in recent weeks that came into effect on April 8.
Shares of vitamin maker Blackmores Ltd BKL.AX , a favourite Australian counter with investors due to booming online sales to China, slumped by as much 18.6 percent to a six-month low on Tuesday, before ending the day down 6.8 percent.
China remains Australia's largest trading partner, despite a slowdown in demand for some exports such as iron ore, and the two nations recently inked a free trade agreement (FTA). However, new rules around imports raise questions about how open the mainland is to foreign companies selling food and health products.
"The market hates uncertainty and the uncertainty that is around this sector at the moment is driving some heavy sell-offs," said Chris Conway, head of research and trading at Australian Stock Report.
Shares of other food and health companies were also hit on Tuesday - infant formula exporter Bellamy's Australia Ltd BAL.AX fell 10.8 percent and dairy exporter MG Unit Trust MGC.AX dropped 8.2 percent.
In contrast, Australia's benchmark S&P ASX 200 gained 0.9 percent.
Beijing ushered in a new tax policy last week that requires products bought on cross border e-commerce platforms to be subject to import tariffs, as opposed to a lower "parcel" tax rate, which they previously enjoyed and had been a major lure for local consumers.
China also published a "positive list" of about 1,200 product types allowed for import via its free trade zones, a move seen as effectively narrowing the scope of a A$100 billion ($76 billion) a year FTA between the two countries, just four months after it took effect.
The new rules come as Australian Prime Minister Malcolm Turnbull prepares to lead 1,000 government and business representatives on a week-long mission to China.
The measures could create more headaches for Turnbull, who faces an election as soon as July amid deteriorating approval ratings, as he tries to improve Chinese access to Australian consumer goods to make up for its faltering demand for Australian resources.
"There is always a risk that protectionist decisions in Beijing, driven by short-term considerations, will have an inordinate impact on Australian exporters," Andrew O'Neil, dean of Griffith University's business school, said in an email.
"The question of how much has really changed with the FTA will undoubtedly persist, stoked by protectionist episodes of the type we've seen recently," he added.
SEEKING CLARITY
Australian exporters say they're awaiting clarification from Chinese authorities around the "positive list".
Blackmores Chief Executive Officer Christine Holgate, who is in the Australian trade mission led by Turnbull, said that while some were concerned by the new regulatory measures, she took them to be a show of "the Chinese government's commitment to free trade". The company's stock had surged 30 per cent from Feb. 26 to the end of last week before falling this week.
"Any clarity is an important step forward," she told Reuters via telephone from Beijing.
Holgate, who will address a dinner of representatives of both countries hosted by Turnbull on Wednesday, said all her company's products appeared on the "allowed" list, and added that a shipment was cleared by Chinese Customs a day earlier.
She said she expects to announce an infant formula partnership with a major Chinese retailer during the trip.
MG Unit Trust said in a statement on Tuesday it noted some of its consumer milk powder and UHT milk products have been removed from sites for immediate sale in China but that it did not expect a material impact on its business.
It too is seeking clarity on the rules and said regulation in China "is very new and likely to evolve".
($1 = 1.3098 Australian dollars)