Yes, an offender can be arrested without a warrant. However, some laws provide that a person cannot be arrested without a warrant. The following persons may arrest without a warrant;
A) A Police Officer; where a person commits an offence in his/her presence, obstructing the officer in execution of his duty etc. see section 10(1) CPA
B) Magistrate, Judge or Justice of the Peace;where the person commits an offence in his presence section 15 ACJL Lagos, sections 24,25 ACJA (2015)
C) Private Persons; if a person in his view commits an indictable offence, reasonably suspects a person has committed a felony or Misdemeanor by night. See section 12 ACJL Lagos, sections 20,21 ACJA (2015) Nweke v. The State (1965) 1 All NLR 114. A property owner or his servant or agent can arrest without a warrant of arrest any person found committing an offence involving injury to his property.