MUMBAI: Fugitive underworld don Dawood Ibrahim 's brother Iqbal Kaskar and his associate were today arrested on charges of extortion and assault , police said.Kaskar and his aide, identified as only Shabbu, were apprehended after being subjected to hours of grilling, said Anil Madvi, Senior Inspector at J J Marg Police Station.The action against the duo came on a complaint filed by a real estate agent, Salim Shaikh. Kaskar, Shabbu and one more person were booked on charges of extortion and assault last night at Byculla Police Station.The complainant claimed Kaskar and his men thrashed him and demanded Rs 3 lakh from him last Friday. The alleged incident had occurred in a room at Damarwala building in South Mumbai's Bhendi Bazar area, police said.The case was subsequently transferred to J J Marg Police Station under whose jurisdiction the incident had taken place.The trio were booked under IPC Sections 385 (putting person in fear of injury in order to commit extortion), 323 (punishment for voluntarily causing hurt) and 34 (acts done by several persons in furtherance of common intention).The 48-year-old victim, a resident of Byculla, first approached the local police station where the FIR was filed and then the matter was transferred to J J Marg police.Kaskar, Dawood's fifth sibling, had been deported to India from the United Arab Emirates in 2003.He was wanted in a murder offence and also for his alleged role in the Sara Sahara case where a building came up illegally on government land. However, Kaskar was acquitted by court in both cases in 2007.