A knock control system for an internal combustion engine, the knock control system comprising: a knock detection unit (50, 60) including at least one knock detection sensor associated with at least one cylinder (26, 26A, 26B, 26C, 26D) of the internal combustion engine, for detecting knocking above a first knock threshold and above a second knock threshold, which is higher than the first knock threshold, during operation of the internal combustion engine; and a knock control unit (50, 90) for controlling operation of the internal combustion engine based on the knocking detected by the knock detection unit (50, 60), the knock control unit being configured to: determine a number of times (n) knocking above the first knock threshold is detected during a predetermined number of combustion cycles in a first operating mode of the internal combustion engine; and when the number of times (n) is greater than a predetermined maximum allowable number of times (nmax) or when knocking above the second knock threshold is detected, cause the internal combustion engine to operate in a second operating mode in which no knocking above a third knock threshold, which is lower than the first knock threshold, occurs, by changing control parameters of the internal combustion engine, wherein the knock control unit (50, 90), after causing the internal combustion engine to operate in the second operating mode, is further configured to cause the internal combustion engine to again operate in the first operating mode after a predetermined time has lapsed since the internal combustion engine was caused to operate in the second operating mode, or when no knocking above the third knock threshold is detected for a predetermined amount of time. a knock detection unit (50, 60) including at least one knock detection sensor associated with at least one cylinder (26, 26A, 26B, 26C, 26D) of the internal combustion engine, for detecting knocking above a first knock threshold and above a second knock threshold, which is higher than the first knock threshold, during operation of the internal combustion engine; and a knock control unit (50, 90) for controlling operation of the internal combustion engine based on the knocking detected by the knock detection unit (50, 60), the knock control unit being configured to: determine a number of times (n) knocking above the first knock threshold is detected during a predetermined number of combustion cycles in a first operating mode of the internal combustion engine; and when the number of times (n) is greater than a predetermined maximum allowable number of times (nmax) or when knocking above the second knock threshold is detected, cause the internal combustion engine to operate in a second operating mode in which no knocking above a third knock threshold, which is lower than the first knock threshold, occurs, by changing control parameters of the internal combustion engine, determine a number of times (n) knocking above the first knock threshold is detected during a predetermined number of combustion cycles in a first operating mode of the internal combustion engine; and when the number of times (n) is greater than a predetermined maximum allowable number of times (nmax) or when knocking above the second knock threshold is detected, cause the internal combustion engine to operate in a second operating mode in which no knocking above a third knock threshold, which is lower than the first knock threshold, occurs, by changing control parameters of the internal combustion engine, wherein the knock control unit (50, 90), after causing the internal combustion engine to operate in the second operating mode, is further configured to cause the internal combustion engine to again operate in the first operating mode after a predetermined time has lapsed since the internal combustion engine was caused to operate in the second operating mode, or when no knocking above the third knock threshold is detected for a predetermined amount of time.