Gasoline prices for all grades rose 3.61 cents in the past three weeks to a national average of $1.68 per gallon, according to a report released Sunday.

With the latest increase, retail prices have risen more than 17 cents a gallon since late December. The Lundberg Survey (search) of 8,000 stations nationwide was conducted Feb. 13.

The price of retail diesel fuel also increased 3 cents to a national average of $1.69 per gallon.

Analyst Trilby Lundberg (search) said several factors were responsible for the hike, including OPEC's (search) decision to cut oil production by 1 million barrels a day beginning April 1, rising crude oil prices and cold weather that increased the demand for heating oil.

Lundberg said the rate of increase is slowing, compared to the previous two weeks before the survey, but there is no indication "prices have peaked or will fall anytime soon."

The national weighted average price of gasoline, including taxes, at self-serve pumps Friday was about $1.65 for regular, $1.75 for midgrade, and $1.84 for premium.