Militants in Nigeria's oil-rich Niger Delta region say none of their fighters have been arrested by the military. On Tuesday, the army said more than 400 men had been arrested following a recent week-long campaign of militant attacks on oil infrastructure. But the Movement for the Emancipation of the Niger Delta (Mend), said the arrests were "random harassment". Mend declared a ceasefire after its campaign of bombings - the most violent the region has seen in two years. Crackdown Mend issued the statement in an email sent by its pseudonymous spokesman Jomo Gbomo. "The military wishes to give the impression they are doing something after the humiliating defeat they suffered," he said. The military commander in Rivers State told journalists his men had found almost all militant camps there, and he would mount a campaign to destroy them. Militant attacks in the Niger Delta have cut Nigeria's oil production by about 20% in recent years. Mend, the most publically visible militant group in the Niger Delta, declared a ceasefire earlier this month, saying they "downgraded the hurricane to a tropical storm". Militants had earlier declared a "war" on Nigeria's oil industry, following a fierce military raid on one of their bases. The attacks forced oil giant Shell to declare a "force majeure", which frees it from contractual obligations on crude oil shipments from its Niger Delta facilities. Groups like Mend claim say they are fighting for more control over oil wealth in the impoverished Niger Delta, but they are accused of making money from criminal rackets and trade in stolen oil. Source: BBC