Turkish police arrested six suspects on Monday during an investigation into the murder of Ali Ekber Akgün, a Dutch citizen of Turkish origin with connections to the Dutch underworld. Two Turkish suspects among six were captured in Istanbul and the capital Ankara for the murder in Istanbul's İstinye district on Dec.24, 2014. Police sources said the DNA samples taken from the car that the gunmen dumped after the murder matched with samples taken from the two men. Four other suspects are held for aiding and abetting the suspects. The suspects denied charges while the manhunt continues for the alleged mastermind of the murder plot. Akgün was gunned down by suspects in a car that was chasing him in his Bentley after he stopped at a red light. The 40-year-old victim was a resident of Istanbul where he migrated to from the Netherlands after a string of trials and police raids targeting him over ties to the Dutch underworld figures and drug trafficking. The police launched a manhunt after the murder and they believe the two suspects, who frequently changed the safe houses they were hiding on, are contract killers. Both suspects had past records of conviction ranging from robbery to inflicting injury. Police are also looking into possible link beetween the murder of Akgün and murder of Vedat Şahin, brother of a notorious Turkish mobster, who was shot dead in Istanbul's Nişantaşı district the day after Akgün's death. Both men reportedly knew each other and Turkish media outlets claimed Akgün had hired Şahin's men for protection against death threats from his connections in the Netherlands.