By Nevzat Devranoglu and Behiye Selin Taner
ANKARA (Reuters) - The Turkish lira plunged as much as 5 percent against the dollar on Thursday as investors continued to fret about moves by Turkish authorities to withhold lira liquidity from the London market.
The central bank has made a series of moves to underpin the lira this week and bankers said it took a fresh step on Thursday, raising its total lira swap sale limit to 30 percent from 20 percent for swap transactions that have not matured.
It had raised the limit to 20 percent on Monday from 10 percent in a move aimed at increasing the bank's forex reserves, which fell sharply in the first two weeks of March.
Those falls have raised uncomfortable questions about Turkey's balance of payments and its ability to roll over foreign loans - and how and from whom it would seek emergency reserves if necessary.
The lira weakened as far as 5.6465 against the U.S. currency from 5.33 on Wednesday. Last year, it plunged almost 30 percent against the dollar.
Brokerage Integral Yatirim said volatility was likely to continue until the elections, making it difficult to identify a clear direction.
The London overnight swap rate plunged to 180 percent on Thursday, Refinitiv Eikon data showed.
On Wednesday it had surged as high as 1,200 percent in what was a stop-gap measure to bolster the lira. That was by far its highest on record, and economists said that level was no longer based on actual trading.
Such rates are a huge hurdle to foreign investors looking to bet against the lira, to hedge or close out positions. They have thus sold off holdings in Turkish stocks and bonds which have came under heavy pressure this week.
The cost of Turkey's debt rose, with the yield on the benchmark 10-year bond climbing to 19.12 percent from 18.21 percent on Wednesday. It has risen 2.5 points since the end of last week.
The main Istanbul share index, which weakened more than 12 percent in the week to Wednesday's close, rose 0.75 percent on Thursday morning.
The head of the Turkish banking association, in a statement to Reuters on Wednesday, said lira swap rates were not surging due to banks withholding liquidity from foreign banks.