ZURICH, April 16 (Reuters) - UBS said on Tuesday it expects low single-digit growth in first-quarter combined net interest income (NII) for wealth management and personal and corporate banking, upping the previous guidance for the two core business arms.

The Swiss lender, which has been under pressure from moves to toughen banking regulation, made the revised projection as it published restated historical segment-level financial data which it said would improve consistency across the group.

The changes include transferring Credit Suisse Swiss Bank high net worth clients from personal and corporate banking to wealth management, and moving all group treasury costs to the business divisions, which were historically retained centrally.

Shares in UBS were down over 3% in early trade as banking stocks across Europe were sold off.

Adding to the heat on UBS were remarks by Swiss Finance Minister Karin Keller-Sutter, who indicated the bank would have to find billions of dollars worth of extra capital under proposals to tighten banking regulation presented last week.

In February, the Zurich-based bank said it expected NII for personal and corporate banking and global wealth management to be roughly flat during the first quarter.

The new guidance reflected how the first quarter had gone, according to a person familiar with the bank's thinking.

UBS declined to comment.

Keller-Sutter told the Tages-Anzeiger newspaper on Tuesday that estimates UBS would need to find another $15 billion to $25 billion under the Swiss government's plan to make the banking sector more robust were about right.

The government's proposals are tailored for banks deemed "too big to fail", particularly UBS, to prevent a repeat of Credit Suisse's collapse last year. The government said UBS would face more stringent capital requirements in future. (Reporting by Paolo Laudani and Dave Graham, Writing by Miranda Murray, Editing by Friederike Heine and Mark Potter)