Is the transaction, which involves the bank purchasing land and then selling it to the customer in installments, with the land mortgaged to the bank until the last installment is paid, and with a known interest rate, considered usury and permissible according to Islamic law?

There is no harm in the land remaining mortgaged to the bank. The Islamic Fiqh Academy has permitted mortgaging the sold item to guarantee the seller's right. Murabaha (cost-plus financing) is permissible if there is an agreement on a known increase over the original price. However, increasing the agreed-upon price due to late payment is not permissible.