The amounts reflected above approximate fair value.

Cash at banks earns interest at floating rates based on daily bank deposit rates. Short-term deposits are generally call deposit accounts and earn interest at the respective short-term deposit rates.

At 30 September 2018, an amount of US$1.6 million (2017: US$1.6 million) was provided as security for a bank guarantee issued in favour of a trade creditor of a subsidiary of the Group and US$0.3 million (2017: US$0.3 million) was provided as security against certain credit facilities of the Group.