PORTSMOUTH - A man brandishing a large knife and wearing a black ski mask robbed the Phillips Route 66 gas station at 2975 Lafayette Road early Monday morning.

He entered the station about 1:30 a.m. and walked behind the counter, stealing an unspecified amount of merchandise. He then fled the scene on foot, according to a police press release. Attempts to locate the man using a K-9 unit were unsuccessful.

Police say the man is white, described as younger, with a medium to thin build, and wearing a black, hooded Boston Bruins sweatshirt with the Bruins logo on the front, a black three-holed ski mask, dark pants, and sneakers, possibly with bright-colored laces.

Police are asking anyone with information to call Detective Scott Study at 610-7653 or Portsmouth Police at 436-2145.

Tips may also be left with Seacoast Crime Stoppers at 431-1199 to remain anonymous. Anonymous tips may also be left online at www.seacoastcrimestoppers.org or by texting an SMS text to CRIMES (274637) and include TIPSCS in the message. Crime Stoppers pays cash rewards of up to $1,000 for information that leads to an arrest and indictment.