Google Inc fell short of Wall Street's first-quarter profit target as operating expenses surged, even though net revenue grew 29 percent year-over-year.

Shares of Google fell about 4 percent to $553.09 in after-hours trade.

The world's No.1 search engine said on Thursday it had net income of $2.3 billion in the first quarter, or $7.04 a share, up from $1.96 billion, or $6.06 a share, in the year-ago period.

Excluding certain items Google said it earned $8.08 a share, below the average analyst expectation of $8.10 a share.

Google's net revenue rose to $6.54 billion in the first quarter, above the $6.32 billion expected by analysts.

Google said the average cost-per-click for its search ads in the first quarter increased about 8 percent year-over-year and decreased 1 percent from the fourth quarter.

(Reporting by Alexei Oreskovic; Editing by Richard Chang)