The Turkish lira took its biggest tumble in more than a year on Monday, while the stock market sank, after Prime Minister Recep Tayyip Erdogan launched a defiant attack against anti-government protesters and warned financial market speculators against exploiting market volatility.

The currency suffered its biggest loss since last May on a closing basis, falling 1.1 percent to 1.8962 a dollar at 12:47 p.m. [5:47 a.m. EDT] in Istanbul, Bloomberg reported.

The Turkish stock market fell on Monday after trading was delayed by an hour, following a glitch. The Borsa Istanbul’s main equity index dropped 1.6 percent to 77,055.75 while Turkiye Garanti Bankasi AS, the biggest Turkish bank in terms of market value, lost 2.5 percent, Bloomberg said.

Turkish markets were volatile last week with the main Istanbul stock index losing almost 15 percent, as protests seeking Erdogan’s resignation raged across the country.

In a series of belligerent speeches over the weekend, Erdogan accused a “high-interest-rate lobby” of economists, stock market speculators and journalists of inciting unrest to manipulate Turkish markets, the Wall Street Journal reported.

“Interest-rate lobby, set yourself in order. For years you have exploited the sweat of my nation. No more... Those who tried to crash the stock market without any shame: Tayyip Erdogan doesn't have money in the stock market, it will be you who will crash,” the prime minister said, warning that government would launch a probe into signs of speculation.

Ratings agency Moody’s warned on Monday that the nation stands at risk of becoming increasingly credit-negative if the protests continue, adding that anti-government sentiment has put the country’s balance of payments at risk, Reuters reported.

The warning came a month after Moody’s raised Turkey to investment grade status. Last November, Fitch gave the country its first investment grade rating, boosting investments in the country.