SEOUL (Reuters) - Samsung Electronics Co reported a record quarterly profit of $8.3 billion and kept its 2013 investment plans at the previous year's level, defying expectations that it may reduce spending amid weaker demand for computer chips.

The South Korean firm said October-December operating profit increased 89 percent from a year ago to 8.84 trillion korean won ($8.3 billion), in line with its earlier estimate.

In a statement on Friday, Samsung said it would keep 2013 investment at a similar level to 2012, despite a bleak PC outlook and a move by rival Apple Inc to diversify its supplier base.

Analysts had expected a 4-20 percent cut in Samsung's capital spending this year.

Samsung, the world's biggest smartphone maker and a key supplier of memory chips, flat screens and microprocessors for Apple's iPhone and iPad, has increased its capital spending every year except 2009 since 2004.

It is preparing for a gradual Apple exit as the Cupertino California-based firm, in a global patent row with Samsung, reduces its component reliance on the South Korean company.

Shares in Samsung have climbed 12 percent over the past three months, while Apple slumped 20 percent, partly hit by worries that its dominance of the mobile industry was waning. ($1 = 1068.7500 Korean won)

(Reporting by Miyoung Kim; Editing by Ryan Woo and Richard Pullin)