NEW DELHI, May 26 (AFP) - India on Wednesday accused Pakistan of stepping up hostile attacks in Kashmir and warned that air strikes would continue until Islamabad-backed Moslem rebels were wiped out. A foreign ministry spokesman said the infiltration of some 400 Pakistan-backed mercenaries and soldiers in Kashmir this month "represents a qualitative upgradation of their hostile activities." "All necessary action will be taken by our armed forces to complete their task of putting an end to this intrusion," the spokesman said. India for the first time used air strikes in Kashmir Wednesday to stop more Pakistan-backed militants from crossing over to the Indian zone of the disputed Himalayan territory. Indian authorities say about 400 Moslem guerrillas, including Afghan Taliban fighters, have infiltrated under cover of artillery fire from Pakistani forces since May 9 and that 160 of them have been killed. "This operation has been obviously undertaken with the full complicity and support of the Pakistan government and the indications are that it involves both Pakistan army regulars as well as highly trained and motivated mercenaries," the official said. "There cannot be a resolution of complex issues or the building of a stable bilateral relationship as long as Pakistan continues to engage in these confrontational and hostile activities," he added. Indian and Pakistani forces have been locked in a new wave of artillery clashes on the Kashmir border since May 9. The spokesman said India had on numerous occasions told Pakistan that its repeated violations of the Line of Control dividing the two countries' parts of Kashmir must stop. "We have called upon Pakistan to abandon this policy ... which is totally counterproductive. Far from accepting our advice Pakistan has chosen to act in the opposite manner. He said Indian caretaker Prime Minister Atal Behari Vajpayee had spoken to his Pakistani counterpart and "Nawaz Sharif's response was that the directors general of military operations should be in contact." "They are already in contact," he added. The spokesman said India always "exercised restraint", in response to United Nations chief Kofi Annan who said Tuesday that he was "concerned" about the situation in Kashmir and called on the two countries to "exercise restraint and cease the fighting."  