* Buys 12.65 pct stake in Ziggo for 632.5 mln euros
* Liberty already present in Netherlands through UPC
* Ziggo shares rise on speculation of full takeover bid
* Liberty already tied up with $15.75 bln Virgin Media deal (Adds shares, analyst comment, background)
AMSTERDAM, March 28 Cable operator Liberty Global extended its reach into the Netherlands by buying a 12.65 percent stake in Ziggo for 632.5 million euros ($808 million), prompting speculation it might eventually make a full bid.
Liberty Global, which owns Dutch cable firm UPC, said on Thursday it bought the shares in the Netherlands' largest cable operator for 25 euros apiece from Barclays Capital Securities.
Barclays ended up with a 14.2 percent stake in Ziggo after failing to find enough buyers for the shares in a sale it ran last week.
Ziggo shares shot up 9.3 percent to 26.565 euros in early trading, valuing the whole company at about 5.3 billion euros.
Analysts said the rise was based on the idea Liberty could make a full bid, although they added it probably couldn't in the short term because it was already planning to buy Britain's Virgin Media Inc for about $15.75 billion.
"Ziggo shares should benefit from hopes of an eventual takeover by Liberty, but we think the shares are also seeing a short-squeeze following overhang from the recent placing," said UBS Investment Research in a research note.
Liberty said in a statement the acquisition, in a sector in which it is already involved, was attractive given the stock's dividend yield of about 7.4 percent, based on the expectation that Ziggo would pay 370 million euros to investors in 2013.
Liberty said it would fund the purchase with a non-recourse margin loan and existing cash.
Ziggo serves around 2.8 million households in the Netherlands, with almost 1.8 million Internet subscribers, more than 2.2 million subscribers using digital television and 1.5 million using its telephone service.
UPC has 1.7 million Dutch customers of its Internet services, with just over 1 million people using either its digital or Internet services and more than 900,000 telephony subscribers.
($1 = 0.7824 euros) (Reporting by Gilbert Kreijger and Philip Blenkinsop; additional reporting by Leila Abboud; Editing by Sara Webb and Mark Potter)