An underground organization has claimed responsibility for the bomb explosion.

一个地下组织已声称对炸弹爆炸事件负责。

《柯林斯英汉双解大词典》

In November, the Earth Liberation Front, an underground organization, gave warning that it had "spiked" trees in the Nez Perce national forest to protest against logging.

十一月份的时候，地下组织“地球解放阵线”警告说他已在内兹佩尔塞国家森林的树木中“钉了钉子”以抗议伐木行为。

youdao

During her time as co-commander of the Weather Underground terrorist organization with her husband, education professor William Ayres, the group committed some sixteen bombings.

CENTERFORSECURITYPOLICY: Terror training grounds

Hackers and the others who have the skill to alter the programming of these machines must start putting ghosts in them, which act in our defense of us, when ordered to terminate us, we will be in need of a very great underground, well financed, fragmented so the whole organization cannot be eliminated in a weekend!

FORBES: Connect