A benchmark lending rate for mortgage loans has risen further.

According to the Korea Federation of Banks on Monday, the COFIX, or the cost of funds index, for outstanding loans climbed zero-point-02 percentage points from last month to one-point-95 percent. The rate for new loans also edged up zero-point-03 percentage points to one-point-96 percent.

The COFIX for outstanding loans is the highest since September 2015. The index for new loans also reached the highest level in three years and nine months.

COFIX is calculated based on the weighted average cost of funding information provided by eight domestic banks.

When the index climbs, the interest on COFIX-linked mortgage loans also goes up, raising the burden on household debt.