NTV television said police in Istanbul had arrested a man described as a leading Hezbollah guerrilla and member of the group's central committee.
The murders have been blamed on Hezbollah, an armed radical group that aims to set up an Islamic state in Turkey.
The bodies were dug out of the basement of a single-storey house in Istanbul, the country's largest city.
The house was thought to be an operational base for the guerrillas. Police continued to search the site, and warned more bodies could be found.
Shallow grave
Nearly 1,000 people have been taken into custody since the nation-wide police operation against Hezbollah began last week, and 39 tortured bodies - mostly the corpses of Kurds - have been recovered from coal sheds and shallow graves.
NTV television said police in Istanbul had arrested a man described as a leading Hezbollah guerrilla and member of the group's central committee.
And in the south-eastern province of Batman, where Hezbollah guerrillas first emerged, police found more than 100 guns in a series of raids.
Blind eye
The find came just hours after Muslim clerics across the country preached a special sermon condemning murder.
The centrally-approved sermon emphasised that taking the lives of others was the greatest sin a Muslim can commit.
Terror, violence and anarchy, it said, had nothing to do with Islam.
The killings have revived accusations that the state turned a blind eye to Hezbollah for years as a buffer against Abdullah Ocalan's Kurdish Marxist separatists.
Correspondents say the mix between Islam and politics is a sensitive subject in Turkey - and the reign of terror attributed to Hezbollah threatens to polarise opinion even further.
The BBC's Chris Morris in Ankara says some argued that the actions of Hezbollah laid the covert agenda of political Islam bare. But moderate Islamists were outraged at this, and said the sudden clampdown had sinister undertones.