Myanmar has been laying landmines in an area of its border with Bangladesh for the past three days, according to reports citing two Bangladeshi government sources.

The sources said the goal of such action may be to prevent the return of Rohingya Muslims fleeing Myanmar.

They noted that Bangladesh will on Wednesday formally lodge a protest against the laying of landmines so close to the border.

The sources, who had direct knowledge of the situation, asked not to be named because of the sensitivity of the issue, Reuters news agency reported.

At least 400 people have been killed and some 125,000 Rohingya Muslims have fled to neighboring Bangladesh since the latest round of violence began in Myanmar’s Rakhine state.

“They are putting the landmines in their territory along the barbed-wire fence” between a series of border pillars, one of the sources said.

Both sources said the issue was disclosed mainly through photographic evidence and informers.

“Our forces have also seen three to four groups working near the barbed wire fence, putting something into the ground,” one of the sources said. “We then confirmed with our informers that they were laying landmines.”

The sources, however, did not clarify if the groups were in uniform, but said that they were sure they were not Rohingya.