LONDON, July 31 (Reuters) - AstraZeneca smashed forecasts for second-quarter sales and earnings on Thursday, demonstrating resilience after seeing off a $118 billion takeover approach from rival drugmaker Pfizer two months ago.

Sales in the first quarter rose 4 percent to $6.45 billion, despite generic competition to some key drugs, generating "core" earnings, which exclude certain items, up 8 percent at $1.30 a share.

Industry analysts, on average, had forecast sales in the quarter of $6.29 billion and earnings of $1.10 a share, according to Thomson Reuters.

On the back of the strong results AstraZeneca said it was raising its guidance for the full year.

Revenue is now expected to be in line with 2013 at constant exchange rates - an increase on previous guidance of low-to-mid single digit percentage decline - and core EPS is set for a low double digit decline, against previous guidance of a percentage decrease in the teens.

(Reporting by Ben Hirschler; editing by Keith Weir)