Samsung Electronics Co. 005930.SE -2.92% on Thursday showed off a cheaper version of its Galaxy S 4 flagship smartphone and new tablets running on the Windows operating system in its bid to gain more market share in the highly competitive mobile-devices market.

The new-product launches come amid mounting concerns that sales of the company's flagship Galaxy S 4 smartphone may not be as strong as the market estimated.

Shares in Samsung, South Korea's biggest company by market capitalization, have fallen sharply over the past two weeks, wiping out more than $27 billion off its market value. The decline in its stock price is reminiscent of the fall in rival Apple Inc. AAPL -1.46% shares earlier this year that was sparked by concerns over demand for its latest iPhone 5.

Morgan Stanley MS -3.68% earlier this month cut Samsung's forecast for Galaxy S 4 shipments to 61 million units this year from 71 million, noting a recent decline in component orders for the phone indicates a 'normal, not super,' global rollout.

The brokerage estimates 310 million smartphone shipments for 2013, compared with an estimated 213 million units shipped in 2012, according to Strategy Analytics. Samsung doesn't disclose sales targets for its smartphones or provide a breakdown of mobile-phone sales.

Samsung is hoping that by launching the Galaxy S 4 mini, the stripped down version of its high-end flagship smartphone, it will be able to grab more consumers especially in emerging markets.

In May, Samsung said it had shipped more than 10 million Galaxy S 4s since the smartphone hit markets in late April. The company hasn't provided sales-figure updates since then.