The gunmen who attacked the camp were riding in a car and on motorcycles. They killed seven soldiers at the camp and a policeman who tried to intercept them, said Mahmood.
The camp near Gujrat was attacked at around 5:20 a.m., a little less than an hour after the leaders of the Difah-e-Pakistan, or Defense of Pakistan, protest movement finished delivering speeches inside the city, said the police.
The group, which includes hardline Islamist politicians and religious leaders, left the city of Lahore on Sunday. They traveled about halfway, spent the night in Gujrat and reached Islamabad late Monday where they staged a rally on the main avenue running through the city toward the parliament.
Police estimated the crowd at 30,000 to 40,000 people. Among the speakers was Hafiz Saeed, who heads what is widely believed to be a front for a militant group that is blamed for the attacks in the Indian city of Mumbai in 2008 that killed more than 160 people.
The U.S. had a $10 million bounty on Saeed, but he operates freely in the country. Pakistan says it doesn't have enough evidence to arrest Saeed, but many suspect the government is reluctant to move against him and other militant leaders because they have longstanding ties with the country's military and intelligence service.
During his speech, Saeed said if the NATO supply routes remain open the U.S. will use it as an opportunity to intervene in the region.
The Pakistani Taliban took responsibility for the attack on the soldiers. A Taliban spokesman, Ahsanullah Ahsan, made the claim to The Associated Press by telephone from an undisclosed location.
The Pakistani Taliban is an umbrella organization created to represent roughly 40 insurgent groups in the tribal belt plus al-Qaida-linked groups headquartered in Pakistan's eastern Punjab province.
The leaders of Difah-e-Pakistan include people with known militant links, including Saeed.
They are not known to be supporters of the Pakistani Taliban, who have waged a bloody insurgency against the state over the past few years.
Many of the Difah-e-Pakistan leaders have strong historical links with Pakistani intelligence, and the group is widely believed to have been supported by the army to put pressure on the U.S. while the government negotiated over the NATO supply line.
Pakistan closed the route in November in retaliation for American airstrikes that killed 24 Pakistani soldiers. The government finally agreed to reopen the supply line last week after the U.S. apologized.
One of the reasons Pakistan waited so long to allow NATO troop supplies to resume was that it was worried about domestic backlash in a country where anti-American sentiment is rampant.
The ruling coalition can ill afford such backlash as it deals with challenges from a powerful Supreme Court.
The coalition pushed a law through parliament late Monday aimed at providing Prime Minister Raja Pervaiz Ashraf and other senior government officials with greater protection from being charged with contempt of court, said Chaudhry Faisal Hussain, a lawyer familiar with the legislation.
The Supreme Court convicted Ashraf's predecessor, Yousuf Raza Gilani, of contempt of court and forced him to step down last month for failing to reopen an old corruption case against President Asif Ali Zardari. Ashraf is keen to avoid the same fate, but the Supreme Court could challenge the new law. The justices have already indicated that they will push the new premier to reopen the corruption case.
Associated Press writer Sebastian Abbot in Islamabad contributed to this report.