Bin Laden was killed in a US-led operation involving helicopters and ground forces in Pakistan on Monday. US officials said bin Laden was found in a million-dollar compound in the upscale town of Abbottabad, 60 km (35 miles) north of the Pakistani capital Islamabad.

'The market did rise early in the day, but then came down amid concerns about the next budget,' said Khalid Iqbal Siddiqui, director at brokers Invest and Finance Securities.

The Karachi Stock Exchange's benchmark 100-share index ended 0.20 percent, or 24.68 points, lower at 12,032.86.

Volume fell to 76.1 million shares from 109.5 million shares traded on Friday.

'I think investors were not too responsive to the news of Osama bin Laden's killing, and they are more worried about what will be there for them in the budget,' said Siddiqui.

Pakistan is expected to unveil its budget for the 2011/12 fiscal year (July June) at the end of May or early June, and investors are worried that the budget may include some measures that could affect investment.

In the currency market, the rupee gained versus the dollar to end at 85.54/64 to the dollar, compared with Friday's close of 84.72/77.

'There was some dollar demand from importers today, but supplies remain healthy,' said a dealer at a foreign bank, and added that the rupee is expected to remain steady near-term.

The rupee has performed strongly in recent months, hitting an 11-month high earlier this month, thanks largely to a record inflow of remittances, strong foreign exchange reserves, healthy exports and a current account surplus, according to analysts and officials.

Remittances by overseas Pakistani increased by 22.37 percent to more than $8 billion in the first nine months of the 2010/11 fiscal year, and in March a record $1.05 billion was received, according to data from the State Bank of Pakistan.

In the money market, overnight rates fell to close at 11.10 percent, compared with Friday's close of 12.50 percent, in a liquid money market.