Sept. 20 (Bloomberg) -- A bomb shattered the Marriott hotel in Pakistan's capital, Islamabad, killing and injuring dozens of guests, many as they ate dinner marking the end of the day's Ramadan fast.

At least 40 people were killed and more than 145 injured in the explosion, Mohamed Wajid, a spokesman for the Edhi Foundation, the city's biggest private ambulance service, said in a telephone interview.

The attack occurred hours after President Asif Ali Zardari made his first speech to parliament, pledging to fight terrorism. Pakistan is battling an Islamic insurgency that left 2,000 people dead last year and has strained the nation's relationship with the U.S. as it and allies fight to subdue Taliban and al-Qaeda forces in neighboring Afghanistan.

Today's blast, which occurred when an explosives-laden truck smashed into the gate of the hotel at 8 p.m., left a 20 foot (6 meter) deep crater at the main entrance. The detonation at the most prominent U.S. business in the Pakistani capital was heard 30 kilometers (18 miles) away in neighboring Rawalpindi.

``The suicide bomber tried to enter from the main gate and blew up his truck,'' Sadruddin Hashwani, who owns the Marriot, told reporters. ``Gas pipelines exploded because of the blast, causing the fire. Some people are still stuck, and we're trying to evacuate them.''

Close to Parliament

A Danish diplomat and three U.S. citizens were among the dead, Dawn News television reported, without saying where it got the information. Four Germans and six Saudi Arabian citizens were injured, the broadcaster said.

The hotel, which has been bombed at least once before, is in the city's high-security zone, less than a kilometer from the parliament building, the President's House and the diplomatic enclave.

The explosion shattered an adjacent government building, shredded trees and smashed more than 40 cars parked near the hotel. More than one ton (2,200 pounds) of explosives was used in the bomb, GEO TV reported, without saying where it got the information.

The blast left a pillar of gray smoke rising into the night sky. Flames were still leaping from the building more than three hours after the incident.

The attackers are ``enemies of Pakistan and enemies of Islam,'' Interior Minister Rehman Malik told reporters in Islamabad.

Breaking Ramadan Fast

The Marriot, a popular place among foreigners and diplomats, was crowded with diners when the bomb detonated. It exploded less than an hour after sunset, the time when Muslims break their fast during the ongoing holy month of Ramadan.

``We were in the main hall serving dinner at the end of the daily fast,'' said Naseer Jahangeer, a waiter. ``The blast destroyed windows and knocked us down. People were screaming.''

There was no immediate claim of responsibility for the attack.

Zardari said in his speech to parliament today that the country won't tolerate any breaches of its sovereignty in the fight against terrorism, reiterating his government's anger at recent raids by U.S.-led forces in Pakistan tribal areas on the border with Afghanistan.

Pakistan has blamed U.S.-led forces in Afghanistan for carrying out attacks on its territory in the past few months and has called for an end to such raids. Pakistan's military has said it reserves the right to retaliate against U.S. raids.

The Bush administration has increased pressure on Prime Minister Yousuf Raza Gilani's government to do more to curb rising militancy.

A group of armed U.S. embassy employees was inspecting the Marriott two hours after the explosion. Dressed in civilian clothes, they wore combat helmets and carried automatic rifles and weren't accompanied by Pakistani police or military officers.

To contact the reporter on this story: James Rupert in Islamabad jrupert3@bloomberg.netBen Livesey in London blivesey@bloomberg.net

Last Updated: September 20, 2008 13:41 EDT