Nearly all the major mortgage lenders in the UK have announced increases in the cost of home loans in recent days.
Analysts are uncertain over whether there are more to come, but are urging people who need to find a new deal to act now.
Someone whose five-year deal is coming to an end faces paying more than £5,000 more a year on their next deal under a typical rate, if they borrow the same amount of money.
Many lenders allow people to lock in a new deal six months before their current one comes to an end, with an opportunity to switch if the costs come down before it kicks in.
"Borrowers expecting mortgage rates to drop in the coming weeks have had their hopes dashed," said Rachel Springall, from financial information service Moneyfacts.
"It is still essential borrowers do not delay seeking advice to navigate the mortgage maze."
For borrowers, the interest rate on a fixed mortgage does not change until it expires, usually after two or five years, and a new one is chosen to replace it. The vast majority of homeowners and buyers have this kind of mortgage.
Since the Iran war began, global economic uncertainty has pushed up the cost of deals.
Someone on a typical two-year deal, and borrowing £250,000 is likely to pay £120 more a month in mortgage repayments than they would have had they secured the deal at the start of March when the US-Israeli strikes began.
More recently, UK government borrowing costs have been rising, which has a knock-on impact on mortgage rates.
That pressure has been maintained in the latest sale of debt by the UK on Tuesday. A 30-year bond issued by the UK was sold with a yield - or interest rate - of 5.82%, the highest since 1998.
The governor of the Bank of England, Andrew Bailey, is expected to be asked about this bond market upheaval when he is questioned by the Treasury Committee of MPs later on Tuesday.
The situation has resulted in several major lenders raising their rates in the last few days.
"The difficult bit is knowing whether this is the end or just the first round of increases," said David Hollingworth, from broker L&C.
Aaron Strutt, of broker Trinity Financial, said: "Hopefully this will be the end of the rate rises for a while, but there are certainly no guarantees.
"Multiple small mortgage price rises add up and ultimately deter people from buying homes."
Potential buyers and borrowers are being urged to seek advice and plan early.
Latest data from the Bank of England shows that more buyers are taking loans with smaller deposits, leaving them more exposed to rate changes.
The proportion of mortgages where the loan is more than 90% of the value of the home has reached its highest level in 18 years.
The latest moves on mortgage rates will be a further blow to those who are coming off much cheaper five-year deals.
However, rates are still some way short of their peaks of recent years, and how much people can borrow, and at what rate, depends considerably on their circumstances.
Moneyfacts said that, as of Tuesday, the average rate on a new, two-year deal was 5.65%. On a five-year product, the average was 5.70%.
