Turkey's embattled lira on Friday plunged to new historic lows in value against the US dollar as markets took fright at a new crackdown against its main pro-Kurdish political party.

The lira is now trading at values substantially lower than in the wake of the July 15 coup aimed at unseating President Recep Tayyip Erdogan which also rattled markets. The detention of a dozen MPs from the pro-Kurdish Peoples' Democratic Party (HDP) overnight put immediate early pressure on the currency and the news its co-leaders Selhattin Demirtas and Figen Yuksekdag had been jailed by a court extended its losses.

The lira was trading at 3.17 to the dollar, a new historic low and a loss in value of 1.8 percent on the day. Its lowest value in the wake of the coup was 3.09 lira to the dollar. The Turkish stock market also tumbled, with the Borsa Istanbul 100 Index shedding 3.15 percent to 74,267 points.

The lira has been under sustained pressure over the last weeks amid doubts over Turkey's flagging growth prospects and fears the drive by Erdogan for a presidential system will risk more instability.