Oversea-Chinese Banking Corp (OCBC), Singapore's second-biggest bank, posted a 21 percent rise in fourth quarter profits, beating expectations.

OCBC's net profit was S$960 million ($683.42 million) in the quarter ended December, compared with S$791 million in the previous year.

Six analysts polled by Reuters had forecast S$872 million in quarterly profits. The upbeat results at OCBC indicate Singapore lenders are yet to be affected by the economic slowdown in China and a slump in oil prices.

"The past year has been a challenging one for most industries. The ongoing economic transformation and slowdown in China have created contradictory pressure on regional economies," OCBC CEO Samuel Tsien said in a statement.

OCBC has significant China exposure following its purchase of Hong Kong-based Wing Hang Bank in 2014. This business accounted for 8 percent of the group's net profit in 2015, Reuters reported.

OCBC said there was a 25 percent rise in bad debt charges from S$154 million in the same quarter in the previous year to S$193 million in Q4 2015.

United Overseas Bank (UOB), the third biggest bank in Singapore, reported a narrow rise in profits this week. The bank said risks are largely manageable as underlying economic fundamentals are strong after reporting a 0.3 percent rise in fourth-quarter net profit.

Singapore's largest lender DBS Group is scheduled to report quarterly results this week.