Aldi to test ecommerce in Britain, other markets - report

* Aldi North mulls online sales in Spain, Portugal - report

* Online grocery sales growing fast in Europe

* Hard to make profit in grocery delivery (Adds Aldi comment)

BERLIN, March 19 (Reuters) - German discounter Aldi , which has long avoided online sales as not profitable enough, is planning to trial ecommerce in Britain and possibly other countries too, including its home market, a trade journal reported on Thursday.

Germany's Lebensmittel Zeitung cited unnamed sources as saying Aldi was preparing to launch an online store in Britain, where grocery ecommerce is more advanced than elsewhere in Europe, already accounting for about 5 percent of sales.

The world's biggest discount chain has offered online delivery of alcoholic drinks in Australia since 2013 but the British test would be its first foray into ecommerce in Europe.

The Lebensmittel Zeitung said Aldi South, which runs the chain in Britain, could go online in other countries including Germany, while sister company Aldi North was considering ecommerce in Spain and Portugal.

Aldi South declined to comment on the article beyond saying the German holding group was not currently planning any online trade, referring queries about Britain to the unit there, which was not immediately available to comment.

Aldi and fellow German discounter Lidl have been expanding rapidly in Britain, stealing market share from incumbents Tesco (Xetra: 852647 - news) , Wal-Mart's Asda, Sainsbury's and Morrisons.

All four incumbents are competing fiercely for a share of the rapidly growing grocery ecommerce market, with Morrisons the last to go online when it struck a deal with ecommerce specialist Ocado last year.

Online grocery sales will roughly double from 2012 to 2016 in five major northern European markets -- Britain, France, Germany, Switzerland and the Netherlands -- the food and consumer goods research group IGD forecasts.

Germany's second-biggest supermarket group REWE said earlier this month it was investing heavily in grocery ecommerce even though it does not expect to turn a profit soon, as it braces for Amazon to expand its food delivery service.

Complex logistics for fresh and frozen produce means it is hard to make online grocery profitable, particularly for retailers selling cut-price goods like those on offer at Aldi. (Reporting by Emma Thomasson; Editing by Mark Potter and Susan Thomas)