Militants said they blew up two more oil pipelines Monday in restive southern Nigeria and called for former US President Jimmy Carter to help mediate an end to the crisis. The Movement for the Emancipation of the Niger Delta, or MEND, said in a statement that fighters hit two pipelines it believes are operated by Chevron Corp. and a Royal Dutch Shell PLC joint venture in southern Rivers state. The militants say they are stepping up their activities after the arrest of one of their leaders, Henry Okah, who is on trial for terrorism and treason. The militants also called for mediation by Carter with the aim of ending the long-running crisis that government-led peace parleys have so far failed to control. The militants have also asked US President George W. Bush and actor George Clooney for their involvement, but said they have received no reply.