Qatar National Bank (QNB) , the Gulf region's biggest lender by assets, made a net profit of 4.5 billion riyals ($1.23 billion) in the third quarter, up 5.4% from a year earlier, Reuters calculated, beating analyst estimates.

The lender reported nine-month net profit of 12.7 billion riyals to Sept. 30, up 7% from the previous year, it said in a statement on Tuesday.

It posted net profit of 8.2 billion riyals for the first six months of the year. Reuters calculated the third-quarter net profit from previous financial statements.

Analysts were expecting a quarterly profit of 3.9 billion riyals, according to LSEG data.

QNB said loans and advances reached 905 billion riyals in the nine months to Sept. 30, up 11% from the same period of last year.

The growth in QNB's loan portfolio helped the bank's total assets to almost 1.3 trillion riyals, up 8% year on year.

Deposits at the lender, which is 50%-owned by sovereign wealth fund Qatar Investment Authority, grew 11% in the period to 909 billion riyals.

Shares of QNB are up over 3% year to date, according to LSEG data.

Last month, QNB Group said it had received regulatory approval for a share buyback, which will be up to 2.9 billion riyals and funded by existing cash resources.

On Tuesday, the bank said it had started the buyback process.

"QNB Group will continue to hold robust capital buffers ... and does not anticipate any material impact on its capital and other ratios because of its intended share buyback," it said on Tuesday.

($1 = 3.6450 Qatar riyals)

(Reporting by Rachna Uppal and Hadeel Al Sayegh; Editing by Mark Potter)