WASHINGTON — Rates on 30-year mortgages edged up slightly this week after falling for three straight weeks.

Freddie Mac, the mortgage company, reported yesterday that 30-year, fixed-rate mortgages averaged 6.62 percent. That was up from 6.59 percent last week, which had been the lowest level since early June.

This week's rate is the highest since 30-year mortgages averaged 6.73 percent four weeks ago, a level that was near the high for the year of 6.74 percent set in mid-June.

The small increase was influenced by developments in financial markets, particularly rates on 10-year Treasury securities, which have the biggest impact on mortgage rates. Analysts said the turmoil in subprime mortgages has not spilled over into the market for conventional loans.

Other types of mortgages also saw rate increases this week.

Rates on 15-year fixed-rate mortgages, a popular choice for refinancing, rose to 6.30 percent, up from 6.25 percent last week.

Rates on five-year adjustable-rate mortgages increased to 6.35 percent, up from 6.33 percent last week, while rates on one-year adjustable-rate mortgages increased to 5.67 percent, up from 5.65 percent.