Shares in Madrid and Lisbon slumped by more than 3.0 percent on Tuesday in line with other European markets hit by fears of a Greek exit from the eurozone ahead of an EU summit. At 1442 GMT, the Ibex-35 index of leading shares fell 3.25 percent to 6,445.1 points. In neighbouring Portugal, the PSI-20 index was down by 3.3 percent to 4,562.93 points.