* Athens' ATG index slides, Greek bank stocks slump
* Germany's Metro falls after Galeria Kaufhof sale deal
* Greek worries impact Italian bonds, Milan FTSE MIB falls
* Europe bourses in 2015: link.reuters.com/pap87v
* Asset performance in 2015: link.reuters.com/gap87v
By Sudip Kar-Gupta
LONDON, June 15 (Reuters) - Greek shares slumped on Monday, as a lack of concrete progress on the country's debt problems pegged back European stock markets.
Athens' benchmark ATG equity index fell 6.2 percent, underperforming a 0.8 percent decline on the broader, pan-European FTSEurofirst 300 index. The ATG is down by around 13 percent since the start of 2015, compared to a 12 percent gain on the FTSEurofirst.
Talks between Greece and its creditors ended in failure on Sunday, with European leaders venting their frustration as Athens stumbled closer to a debt default that threatens its future in the euro.
The Athens stock market has been especially volatile, surging one day on prospects of an agreement only to then fall back as those expectations have been dashed.
The ATG index had already fallen 5.9 percent on Friday, and Greek bank shares bore the brunt of the new sell-off on Monday.
The Athens Stock Exchange FTSE Banks Index dropped 12.5 percent, with National Bank of Greece falling 11.6 percent and Bank of Piraeus slumping 16 percent.
"There's been no progress on Greece, so I expect European stock markets will undergo further selling pressure in the near-term," said Berkeley Futures' associate director Richard Griffiths.
Germany's DAX retreated 1.1 percent to 11,071.53 points, leaving the index some 11 percent below a record high set in April, while France's CAC declined by 1 percent.
German retailer Metro was among the worst-performing stocks, retreating 3.8 percent after agreeing to sell its Galeria Kaufhof chain to Canadian department store operator Hudson's Bay for 2.8 billion euros - less than some estimates of a 2.9 billion euros price tag for Galeria Kaufhof.
Italy's FTSE MIB equity index fell 1.6 percent, with banking group Intesa Sanpaolo dropping 2.5 percent as worries over Greece's debt situation hit the Italian bond market.
Economic stimulus measures and record low interest rates from the European Central Bank (ECB) have cushioned some of the blows to European stock markets from Greece so far this year.
The DAX and CAC both remain up by around 13 percent, but traders said investors could quickly sell out of any stock market rallies while the Greek situation remained unresolved.
"Sentiment remains negative with rallies likely to be sold until there is some positive news what a Greek deal is concerned," said Peregrine & Black senior sales trader Markus Huber.
Today's European research round-up (Editing by Kevin Liffey)