Is zakat obligatory on leased properties from which no income is generated, or on unleased properties, given the current circumstances?

We ask Allah to grant victory to our brethren in Palestine and to bestow tranquility upon them. Leased or vacant properties are not subject to zakat (definition). Zakat is due only on their rent, provided it reaches the nisab (definition) (minimum threshold) and a hawl (full lunar year) has passed. If the rent is a debt owed by tenants and has reached the nisab, zakat is due on it for one year only upon its receipt, even if it remained outstanding for several years.