Karachi- Protests broke out both on and off the trading floor Thursday in the southern port city of Karachi as Pakistan's largest stock market plunged, traders said.

Hundreds of investors and traders shattered windows and hurled stones at the stock exchange building after the benchmark Karachi Stock Exchange 100 Index slid 278 points, or 2.6 per cent, to close at 10,212.

Most of the protesters demanded an immediate closure of the market after two months of falls have driven hundreds of them to the verge of insolvency.

The Pakistani market has lost about 30 per cent of its value since the beginning of the year, eroding around 22 billion US dollars in market capitalization on mounting economic and political uncertainties.

Rising tensions with neighboring Afghanistan and threats from Kabul and international forces in Afghanistan to launch a major operation against Islamic militants inside Pakistani territory were also discouraging investors.

Adnan Afridi, managing director of the Karachi bourse, called demands to close the market nonsense.

"There is no way we will close the market," Afridi said.

A senior official of the state corporate watchdog, the Securities Exchange Commission of Pakistan, also rejected demands for the suspension of trading to save few investors.

The commission had tried to keep the market afloat for the past month by instituting restraints, such as an automatic suspension of any shares that decline more than 1 per cent.

The restrictions were lifted Monday, and since then, the benchmark index had lost more than 1,000 points. (dpa)