It says the attacks are taking place despite security forces being deployed to Benue State.
It's reported 500 people died during the attacks and according to Senator David Mark "all the primary and post primary schools, health centres, worship centres as well as the police station in the area have been burnt down."
After visiting the area, Angele Dikongue-Atangana, the representative of the United Nations High Commissioner for Refugees (UNHCR) and the Economic Community of West African States (ECOWAS) to Nigeria, remarked that in 20 years of working as a humanitarian she had "never seen such a level of destruction".
CSW is also raising concern over attacks in the south of the country. It says last week, Revd Father Aniako Celestine from St Joseph's Catholic Church Ukana in the Udi LGA of Enugu State was kidnapped by suspected Fulani herders while travelling to his home in Ezeagu LGA.
According to local media reports, the kidnappers used the priest's mobile phone to demand a N10 million (approximately £35,500) ransom for his release.
Chief Executive Mervyn Thomas said: "It is deeply worrying to hear that communities in Agatu are still under siege weeks after security forces were sent there.
"The geographical range and scale of violence involving Fulani herders, and the proliferation of small arms, indicate that it has mutated far beyond inter-communal competition for resources into a significant threat to national security.
"Addressing this violence must become a priority, with attacks being met by an effective defence of besieged communities, as well as of herders who are legitimate victims of cattle rustling.
"Murder, rape, and destruction of personal and federal property are criminal acts; consequently, perpetrators ought to be apprehended, disarmed and prosecuted in order to combat lawlessness and impunity. In addition, given the significant sensitivities generated throughout the country, it is vital that the potentially explosive issue of grazing reserves is handled with extreme caution and objectivity."