KARACHI - Muttahida Quami Movement chief Altaf Hussain on Thursday telephoned Federal Interior Minister Rehman Malik and expressed concerns over the killings of his party workers.Hussain told Malik that five MQM men were killed in the provincial capital in the last three days. He demanded arrest of target killers and stepped up efforts to curb the menace of target killing, saying that the government should adopt effective measures to main law and order. Malik expressed his sympathies with Hussain and assured him of bringing the culprits to justice.