Nassau County police said they are stepping up patrols near the areas where a man used a machete to rob a Seaford store Wednesday night, about half an hour before another attempted robbery involving a machete at a store in South Farmingdale.

“It’s always very concerning to us because of the fact that’s it’s a very dangerous instrument, it’s a dangerous weapon,” Det. Lt. Richard LeBrun said at a news conference at police headquarters on Thursday.

The man first entered the Dunkin’ Donuts on Merrick Road in Seaford at 9:12 p.m. Wednesday, displayed the machete and demanded money, police said. After being told there was no money, the man fled through the parking lot, police said.

In that incident, he was described as 5-foot-7 and wearing a black hat, a dark-colored jacket, black and white sneakers and black gloves.

Police said they believe the same man entered the Carvel store on Northwest Drive in South Farmingdale at 9:43 p.m., displayed a machete and demanded money.

The cashier, who had been counting money in the tip container, handed him that money — about $40, police said. He then ran north on foot on Hart Street, police said.

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The cashier was one of three young women working in the store at the time of the robbery, LeBrun said.

The Carvel robber was described as wearing a dark-colored jacket, a black ski hat and white sneakers, and had a gray scarf covering his face.

“Please do not try to fight him off,” LeBrun advised store owners and workers who may be targeted in the future. “Please give him the cash and hopefully he will be on his way. Immediately call 911.”