A San Francisco-based online food and grocery shopping and delivery service is staking a claim in Connecticut.

Instacart is set to launch Thursday in the state, offering shopping services to Bridgeport, Stamford and other towns. Residents of Hartford, East Hartford, West Hartford, Enfield, Manchester and other municipalities also will be able to go online or use an app to order supermarket items for delivery to their doorstep as soon as one hour later.

Founded five years ago and backed by private financing, most recently $400 million, Instacart operates in 50 markets in the United States, said Kyle Carnes, operations manager. Competition is stiff and includes Amazon, Peapod and online shopping offered by supermarkets.

Internet supermarket shopping is a "tiny piece" of the $800 billion grocery market, Carnes said.

Customers pay $5.99 for a delivery or can purchase a membership for $14.99 a month or $149 a year. They can order from Big Y, BJ's, Costco, PriceRite and Whole Foods Market.

Instacart shoppers are trained in how to pick the best produce, get the orders right at the deli and other supermarket tasks. They also are tested in food safety, Carnes said.

Customers can go to Instacart.com or open the Instacart mobile app, select their city and store, add items they want and choose delivery within one hour, two hours or up to seven days in advance.

Customers are diverse, from young professionals too busy to shop to the elderly who can't easily get to a supermarket, Carnes said.