Shares in troubled Italian bank Monte dei Paschi di Siena are rising after the board confirmed Merrill Lynch banker Marco Morelli as its new CEO.

The world's oldest bank, which has been struggling to relaunch itself following a period of scandal and mismanagement, saw its share price rise 2.4 percent to 0.23 euros in Thursday trading.

Morelli replaces Fabrizio Viola, who unexpectedly resigned last week, ahead of a planned 5 billion-euro ($5.6 billion) capital increase.

Pressure has increased on Italy's third-largest bank by assets after it emerged as the worst performer in EU-wide stress tests in July.

The board also announced that Chairman Massimo Tononi is resigning "after having managed the process of appointing the new chief executive officer."