Office rent rates in Vietnam's biggest cities, HCM City and Hanoi, are among the highest in over 100 markets worldwide, according to an annual report released by British real estate services firm Knight Frank last week.

HCM City is the 19th and Hanoi the 21st most expensive markets with prime rents at 38 USD and 36.5 USD per square metre per month respectively, the report said.

The rates are more expensive than established markets like Manhattan ( New York , US ), Frankfurt ( Germany ), Shanghai ( China ), Brussels ( Belgium ) and Rome ( Italy ).

However, availability has increased in Vietnam , with both the cities seeing large amounts of new Grade A office supply during 2010. This has caused vacancy rates to rise and put pressure on Grade A rents. Meanwhile, demand remains strong in the Grade B and C office sectors, according to the report.

Elsewhere, rental growth has been led by the world's major financial centres, with office rents rising in cities such as London , New York , Hong Kong and Singapore , said the report.

In contrast, rents continue to come under downward pressure in a smaller group of markets, including Los Angeles, Madrid, Seoul and Dubai, where the economic outlook remains uncertain or availability of space is high./.