South Korea's central bank froze the key interest rate for the sixth straight month on Thursday in an apparent bid to preserve policy room for rainy days, rejecting the government's call to join the stimulus drive.

Bank of Korea (BOK) Gov. Kim Choong-soo and his fellow policymakers left the benchmark seven-day repo rate unchanged at 2.75 percent. The bank lowered the borrowing costs in July and October last year.

The decision was not anticipated as only two out of 25 analysts predicted the rate freeze for April in a poll made by Yonhap Infomax, the financial news arm of Yonhap News Agency.

The move comes even after the BOK has been under mounting pressure by the government to lend support to its stimulus actions on concerns over a low growth trend.

The new government of President Park Geun-hye sharply cut its 2013 growth projection to 2.3 percent from 3 percent last month, vowing to implement strong stimulus packages, including an extra budget. The BOK's current 2013 growth estimate stood at 2.8 percent.

"The government will unveil what will be one of the largest fiscal supplementary packages. ... We estimate the fiscal impulse similar to three rate cuts, so the fiscal stimulus could crowd out monetary easing in the short term," said Waiho Leong, a senior economist at Barclays Capital.

The rate freeze indicates that the BOK's assessment of the growth path has not largely changed compared with a month earlier and heightened geopolitical risks from North Korea may not be serious enough to dent the economic growth, analysts say.

Gov. Kim has cast a relatively positive assessment of economic conditions, saying that the local economy will not deteriorate further and even expressed concerns about a long streak of low rates.

The minutes from the bank's recent policy meetings showed that some BOK board members have raised questions about the effectiveness of a rate cut in shoring up the economic growth.

While the U.S. and China are showing some signs of economic recovery, a set of economic data at home are sending mixed signals about the strength of the recovery. Korea's industrial output shrank for the second straight month in February while exports managed to chalk up an on-year gain in March.

The April policy meeting has been in the spotlight as it could become a litmus test for the central bank's autonomy in managing the monetary policy.

The finance minister, a chief presidential economic secretary and the floor leader of the ruling party have recently made remarks interpreted as putting pressure on the BOK to issue a rate cut, hurting the central bank's independence.

Finance Minister Hyun Oh-seok said Monday that the rate decision is in the hands of the BOK board members but added that when fiscal and monetary policies are coordinated, the effects of the policy mix will increase.

The finance ministry decided not to send its vice minister to the BOK's rate-setting meeting starting this month, a practice that had been in place since January 2010, apparently mindful of growing criticism.

Analysts are divided over the BOK's next move, but more experts cautiously expected that the BOK may freeze the benchmark rate for the rest of this year as the local economy is likely to pick up in the second half.

The central bank earlier said that Asia's fourth-largest economy will likely grow 3.5 percent in the second half after rising 1.9 percent in the first half.

But the local bond market has already priced in chances for rate cuts this year, with the yield of three-year government bonds hitting a record low of 2.44 percent on April 5. (Yonhap News)