Feb 12 (Reuters) - New York Community Bancorp shares surged on Monday, extending a rally from the previous session after top executives disclosing they had bought stock in the U.S. lender.

The bank has been looking to boost investor confidence to stem a selloff in its shares that began on Jan. 31, when it posted a surprise quarterly loss due to its loans tied to the stressed commercial real estate (CRE) and slashed its dividend.

Purchases by NYCB executives totaled more than $850,000 combined, regulatory filings published on Friday showed.

The stock was last up 9% in early morning trading. It had closed up 17% on Friday. Still, they are down 50% so far this year and have weighed on the banking sector.

The KBW Regional Banking Index, a key index to gauge investor sentiment toward the sector, has lost 10% in the same period.

Investors worry that weak demand for offices could trigger a wave of defaults in the U.S. office property sector and hurt the balance sheets of banks, which are hoping to avoid selling CRE loans at significant discounts.

Brokerage Morgan Stanley said there will be a need to refinance about $2 trillion of CRE debt - half of which is on bank balance sheets - expected to mature by the end of 2025.

"Our work indicates that the top 25 banks have about 30% of this exposure and the rest of the 4,500+ smaller, regional banks have the remaining 70%," it said in an industry note.

Last week, banking veteran Alessandro DiNello, who was appointed NYCB's executive chairman, said the bank will consider the sale of loans in its CRE portfolio or allow them to run off the balance sheet naturally.

(Reporting by Manya Saini and Niket Nishant in Bengaluru; Editing by Arun Koyyur)