Samsung Electronics Co Ltd recently approached BlackBerry Ltd about buying the smartphone maker for as much as $7.5 billion in a play for its patent portfolio, according to a person familiar with the matter and documents seen by Reuters.

South Korea's Samsung proposed an initial price range of $13.35 to $15.49 per share, representing a premium of 38 percent to 60 percent over BlackBerry's current trading price, the source said.

Executives from the two companies, which are working with advisers, met last week to discuss a potential transaction, the source said, asking not to be identified because the conversations are private.

It remains unclear whether Blackberry, which has regained some of its lost swagger under CEO John Chen over the past year or so, was open to the approach. Representatives for the company declined to comment.

News of the meeting, which sent Blackberry shares up nearly 30 percent, comes as the smartphone maker looks for renewed growth and for how to regain market share it has lost to Apple Inc, Google Inc and Samsung.

A deal would give Samsung access to Blackberry's patents, which the source said would help it take on arch rival Apple.

Any tie up with Samsung would have to have the blessing of Prem Watsa, whose Fairfax Financial Holdings Ltd is a major Blackberry shareholder. Fairfax helped bankroll a debt recapitalization that led to Chen's arrival in November 2013 as CEO of the one-time investor darling that pioneered the smartphone.

BlackBerry launched its long-awaited Classic model on Wednesday, hoping to help win back market share and woo customers still using older devices with a keyboard. The phone resembles its once popular Bold and Curve handsets.

In the third quarter, revenue at Blackberry fell to $793 million from $1.19 billion a year earlier, falling short of analysts' expectations of $931.5 million.

Shares of Blackberry jumped as much as 30 percent on heavy volume in afternoon trading at $29.71 per share in New York.

The offer price would imply an enterprise value of $6 billion to $7.5 billion for BlackBerry, assuming conversion of $1.25 billion of convertible debt, according to the documents.

BlackBerry announced a high-profile security partnership with Samsung in November. The partnership will wed BlackBerry's security platform with the South Korean company's own security software for its Galaxy devices.

Representatives for BlackBerry declined to comment while Samsung and Fairfax could not be immediately reached for comment.