Samsung on Thursday (April 25) launched the latest version of its flagship Galaxy S4 smartphone in Seoul.

Samsung said the phone would go on sale on Friday (April 26) in its home country's market first, and that it would be available in more than 150 countries by the end of April.

Samsung's "S" line of smartphones has spearheaded its assault against Apple in past years and was instrumental in helping the company claim top-spot in the global smartphone market.

The new S4, which sports a host of software-enabled features, is seen as stealing a head start on what's widely expected to be an upgraded iPhone later this year.

But the phone has drawn mixed reviews so far.

The Wall Street Journal's Walt Mossberg, a widely followed gadget impresario, said the S4 was a good phone, just not a great one.

Industry watchers have said the success of the S4 could hinge on a supply back-up plan aimed at preventing a repeat of costly problems encountered in the launch of its premium smartphone last year.

Some analysts predict the new Galaxy could top 10 million unit sales in the first month after its launch, so any hiccups in the smooth delivery of core components could be disastrous.

The risks are high. A simple manufacturing error involving unsatisfactory design of handset cases cost Samsung two million units of lost sales in just a month after it launched the S III in May last year.

Presented by Adam Justice