TRENTON, N.J.—Gas prices increased in New Jersey and around the nation at large amid increased demand as warmer spring weather lures motorists back out onto the roads, analysts said.

AAA Mid-Atlantic says the average price of a gallon of regular gas in New Jersey on Friday was $3.25, an increase of two cents from last week. Drivers were paying $4.19 a gallon on average a year ago at this time.

The national average price for a gallon of regular gasoline was $3.50, up six cents from last week. Drivers were paying $4.22 a gallon on average a year ago at this time.

Analysts say tightening gasoline supplies and signs of slowing inflation have pushed oil prices above the $70 per barrel mark, and that and robust gas demand are likely to send prices at the pump higher for the time being.