Any Member State which has entered a reservation under paragraph 3 shall make extraditable under the terms of Article 2 (1) the behaviour of any person which contributes to the commission by a group of persons acting with a common purpose of one or more offences in the field of terrorism as in Articles 1 and 2 of the European Convention on the Suppression of Terrorism, drug trafficking and other forms of organised crime or other acts of violence against the life, physical integrity or liberty of a person, or creating a collective danger for persons, punishable by deprivation of liberty or a detention order of a maximum of at least 12 months, even where that person does not take part in the actual execution of the offence or offences concerned; such contribution shall be intentional and made having knowledge either of the purpose and the general criminal activity of the group or of the intention of the group to commit the offence or offences concerned.