Advertising firm

WPP Group

( TFSM) has agreed to acquire

24/7 Real Media

( TFSM) for about $649 million.

David Moore, CEO of 24/7 Real Media, said in a press release Thursday that the "transaction further validates the importance of emerging, digital media to the global advertising market and 24/7 Real Media's role in strengthening the role of digital media among WPP companies."

The deal, which places a 4% premium on 24/7 Real Media's market cap, given a recent run-up in the stock on hopes of an acquisition, extends the wave of deals taking place in the online ad space.

Recent weeks have seen the $3.1 billion

acquisition of privately held DoubleClick by

Google

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, and the $680 million deal by

TheStreet Recommends

Yahoo!

( TFSM) to acquire the remaining stake in Right Media.

Many onlookers also expect

Microsoft

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, which had initiated talks with DoubleClick, to take out another company in the near future.

Shares of 24/7 Real Media gained 3.8% on the news to $11.69. Shares of

ValueClick

(VCLK)

and

aQuantive

( AQNT), two other online advertising concerns, also gained 2.6% and 3.5%, respectively, in early Thursday trading.