The average national price of gasoline rose nearly 12 cents in the past three weeks, marking the first price hike after six months of steady decreases, according to a national survey released Sunday.

The increase was even steeper in Washington state, rising 20 cents or more over the past month in some cities.

Nationwide, the average price of regular gasoline was $1.78 a gallon on Friday, oil industry analyst Trilby Lundberg said. The price of mid-grade was $1.91 a gallon and the price of premium was $2.02 a gallon.

The increase was the first since July 11, when the average national price peaked at $4.11 a gallon.

Of cities surveyed, the nation's lowest price was $1.34 in Billings, Mont. The highest price was $2.32 in Anchorage, Alaska.

In Seattle, the average price of regular gas was $2.03, edging above $2 for the first time in weeks, according to AAA. That marked a 20-cent increase in the past month, but it was still far below Seattle's peak price of $4.39 a gallon, set last June.

Statewide, the average price for regular was $1.95 a gallon. The cheapest gas in Washington was in Spokane, where it stood at $1.59 a gallon for regular on Sunday.