Libyan rebels were mourning the killing of its military leader amid an intensified conflict with troops loyal to Muammar Gaddafi, as the country's humanitarian situation worsens with a new wave of refugee exodus. Abdel Fattah Younes, Gaddafi's former security minister who defected to the opposition Transitional National Council (TNC) and became its military leader in February, was shot dead by assailants after being summoned back from the battlefield, opposition leader Moustafa Abdel-Jalil said. A three-day mourning was planned for Younes in the rebels' stronghold of Benghazi. The death was announced as the rebel forces launched a broader assault on government forces Thursday, seizing three small towns in western Libya while advancing toward the town of Badr and two other areas. Meanwhile, the TNC was recognized as Libya's legitimate representative by more countries, installing ambassadors in Paris and London on Thursday to formalize ties with its main allies in the fight to topple Gaddafi. Rejecting UN envoy Abdel Elah al-Khatib's proposals for ceasefire and a power-sharing government, Jalil told Xinhua in an interview that the removal of Gaddafi and his followers from office is the prerequisite for any political solution to the Libya crisis. In the United Nations, B. Lynn Pascoe, under-secretary-general for political affairs, said Thursday that the UN should remain poised to help Libya, as the northern African country faces major obstacles to peace and security. "The challenges posed by the crisis in Libya are serious ones, but we believe they can be managed by staying closely involved, actively pursuing a negotiated solution, and planning carefully for a possible role, if asked, in the future," Pascoe told the UN Security Council as it held consultations on the situation in Libya. Pascoe said the humanitarian situation on the ground in Libya continues to worsen. Up to 630,000 people have left the country since the conflict began, and 200,000 have been internally displaced throughout the country. More than 1,000 people have died trying to escape from Libya to Europe. As the Libya war drags on, at least 6,000 refugees fled Libya Wednesday into Tunisia through the Ras El Jedir border point. More refugees are expected to cross into Tunisia in the wake of the escalation of violence in Libya, Tunisia's official news agency TAP said.