European stocks advanced, sending the Stoxx Europe 600 Index to its highest level in more than a month, amid speculation the Federal Reserve will expand Operation Twist to help sustain economic growth.

Euro-area leaders at the Group of 20 summit in Mexico yesterday pledged to take “all necessary policy measures” to defend the currency union as world leaders endorsed a road map for tighter integration to cut borrowing costs and prevent further damage to the global economy. Attention now shifts to a summit of European Union leaders in Brussels on June 28-29.

National benchmark indexes rallied in all 18 western- European markets except in Switzerland and Ireland. The U.K.’s FTSE 100 Index added 0.6 percent and Germany’s DAX increased 0.5 percent. France’s CAC 40 increased 0.3 percent.

Aer Lingus paced advancing shares after Ryanair, Europe’s biggest discount airline, offered to buy its Irish rival for 694 million euros ($883 million). Aer Lingus surged 15 percent to 1.09 euros in Dublin, the most since September 2009, as Ryanair, which already holds a 29.8 percent stake, said it intends to make an all-cash offer of 1.30 euros per share.

H&M gained 4.8 percent to 241.50 kronor after Europe’s second-largest clothing retailer reported a 23 percent increase in second-quarter profit to 5.22 billion kronor ($751 million) as U.S. and Asian sales rose. The average of 14 analysts’ estimates compiled by Bloomberg called for 4.86 billion kronor.

Kesa Electricals Plc dropped 5 percent to 52.5 pence after the owner of the Darty electronics chain reported a 42 percent slump in full-year adjusted pretax profit to 59 million euros. The company cut its dividend and said Mothercare Plc’s Alan Parker will replace David Newlands as chairman. The shares had climbed 19 percent over the previous four days.