** Shares of European oil and gas cos fall 2-5 pct aftercrude dropped as much as 6 pct earlier on Monday
** Output freeze meeting by major producers in Qatar fellapart after Saudi Arabia demanded Iran to join the deal
** Stoxx oil & gas index falls >3.5 pct wiping offYTD gains - on track for its worst day in nearly 2-1/2 mths
** BP (-3.4 pct), Total (-3.5 pct), Shell and Statoil (-4 pct) are among the biggestdrags on the oil index
** Repsol SA (-4.1 pct), Amec Foster (-5.8pct), Subsea 7 (-4.8 pct) and Tullow Oil (-6pct) are among the top fallers on pan-European Stoxx 600 index
** Stocks are nearly wiping off all their gains from lastweek's rally that based hopes on the Doha deal
** Brent and WTI pare some losses to tradedown 5 pct (RM:thyagaraju.adinarayan.thomsonreuters.com@reuters.net)