BOSTON — Massachusetts gas prices have risen 2.1 cents per gallon in the past week, averaging $2.56 per gallon on Monday, according to GasBuddy's daily survey of 2,830 stations.

Gas prices in Massachusetts are 6.4 cents per gallon lower than a month ago, yet stand 28.7 cents per gallon lower than a year ago.

The national average price of gasoline has risen 8.5 cents per gallon in the last week, averaging $2.66 per gallon Monday. The national average is up 7.3 cents per gallon from a month ago, yet stands 17.4 cents per gallon lower than a year ago.