Maoist rebels in Nepal have officially announced the end of their unilateral four-month cease-fire, saying they need to defend themselves against Government forces. The move has come despite calls from opposition parties and human rights groups for it to be extended. The truce has not been matched by the forces of Nepal's King Gyanendra, who sacked the Government and assumed its powers in February. "The royal army is surrounding our people's liberation army, which is in defensive positions, to carry out ground as well as air attacks on us," Rebel chief Prachanda said in a statement. "Therefore, we are compelled to go on the offensive, not only for the sake of peace and democracy but for the sake of self defence," he said. The Nepalese Government has not given an immediate comment but has in the past said the rebels use cease-fires to regroup.