Is buying shares from a bank in installments and then selling them for less than the purchase price considered usury (riba)?

It is not permissible to buy shares from an interest-based (riba-based) bank, nor is it permissible to deal with it at all. However, if the bank operates according to the rulings of Islamic Sharia, then there is no objection to buying and selling shares from it, provided there is no other impediment.