Yemeni security officials say that Oman has closed its two border crossings with Yemen over fears of militant attacks, leaving Yemenis largely sealed off from the outside world.

Three security officials from the eastern province of Mahra, which borders Oman, told The Associated Press on Wednesday that the closure took place earlier this year, but did not give specific dates. They spoke on condition of anonymity because they were not authorized to speak to the press.

The crossing was the only unrestricted passage still open for Yemenis. Except for Sanaa airport, airports and borders with Saudi Arabia were closed months after a Saudi-led military campaign against Houthi rebels in Yemen.

Militants affiliated with Islamic State group have claimed responsibility for some of the bloodiest attacks against government officials and rebels.