Hundreds of small investors demonstrated at Pakistan's main stock exchange Thursday, breaking windows and burning tyres, after another day of heavy losses in trading, officials and witnesses said.

Police and the military were called in to restore order at the Karachi bourse where the 100-index has been on a steep decline for the past two weeks amid growing political uncertainty, dealers said.

The benchmark Karachi Stock Exchange (KSE) index of 100 shares shed another 279 points to close at 10,212 points, representing an 18-month low, about 36 percent down from an all-time high in April.

Investors in Lahore and Islamabad held similar protests, burning tyres and blocking roads, witnesses said.

The market is under pressure due to political uncertainty, a liquidity crunch and foreign selling, dealers said.

The KSE had peaked at more than 15,000 points in April and the capitalisation is down from 71 billion dollars to around 50 billion dollars.

Analysts fear the trend is likely to continue.

"The institutional support has started, but the situation could last for some time because of deteriorating Pakistan-Afghanistan relations and tension on our northwestern borders," senior analyst Azhar Ahmad Batla said.

"The market has shed more than 1,300 points (around 15 percent) since start of this week," Batla told AFP.

Witnesses said more than 200 small investors, some of whom rent small offices in the exchange building, gathered in its main hall to demand a halt in trading.

When the exchange administration declined, some protesters smashed windows, said Mohammed Aslam, the exchange's security chief.

The police said they made no arrests and the situation was under control.

The stock exchange administration also called paramilitary Rangers to help the police.

"Our personnel are there to keep the situation under control," Rangers spokesman Major Mohammad Ali Malik said.

AFP