A method of igniting a fuel within a combustion chamber defined by a cylinder block of an internal combustion engine includes injecting a first portion of a fuel into the combustion chamber, and energizing a first plasma igniter. The first plasma igniter is configured for generating a first plurality of free radicals, extends through a cylinder head mated to the cylinder block, and protrudes into an intake port defined by the cylinder head that is disposable in fluid communication with the combustion chamber. After injecting the first portion, the method includes activating a second igniter configured for initiating a flame within the combustion chamber to thereby ignite the fuel. The second igniter extends through the cylinder head and protrudes into the combustion chamber. An internal combustion engine is also disclosed.