Addressing a press conference here, Chidambaram said, "There are bazaars across the border. You can always get arms from there. Where do you think northeast rebels are getting the arms from."
Chidambaram said that India shared an open border with Nepal, Bangladesh and Myanmar through which the rebels were clandestinely smuggling weapons.
"Moreover, they received money from extortion and looting banks," he said.
The Home Minister further said that anti-Naxal operations might need to be reviewed but that was entirely up to the operational commanders.
Chidambaram said an inquiry has been initiated into the Dantewada incident to find out what went wrong.
"We will launch a full probe into what went wrong, look into the lapses," he said.
In 2009, Home Secretary GK Pillai had said that the Naxals were getting arms from illegal weapons markets in China, Myanmar and Bangladesh.