Further, more than one militant was killed in a bomb blast.

Correct: The original sentence "Further, more than one militant was killed in a bomb blast." is correct.

Explanation: The phrase "more than one" is followed by a singular verb, so "was" is the correct verb form here.

• Rule: "more than one" + singular noun takes a singular verb. Example: "More than one student was present."

• Why "were" is wrong: "were" is plural, so "more than one militant were killed" is incorrect; use "was killed."

• Why the other alternatives are wrong: "are killed" uses present tense and is unsuitable for a past event; "have been killed" uses a plural auxiliary and should be "has been killed" if one insisted on the perfect aspect, though the simple past "was killed" is clearest.

Note: For formality, you may prefer "Furthermore" instead of "Further," but this is optional and does not affect the subject-verb agreement.