Gunmen killed seven people Monday at a Pakistani army camp in a city where thousands of hardline Islamists spent the night on their way to the capital to protest the government's recent decision to reopen the NATO supply line to Afghanistan, security officials said.

Police are searching for the culprits, and it's unclear whether any of the Islamist protesters were involved, said an army officer and three policemen, speaking on condition of anonymity because they were not authorized to talk to the media.

The camp on the outskirts of the eastern city of Gujrat was attacked around 5:20 a.m., a little less than an hour after the leaders of the Difah-e-Pakistan, or Defence of Pakistan, protest movement finished delivering speeches inside the city, said two of the policemen.

The group, which includes hardline Islamist politicians and religious leaders, left the city of Lahore on Sunday along with 8,000 supporters in 200 vehicles to make the 300-kilometre journey to Islamabad. They traveled about halfway, spent the night in Gujrat and plan to hold a protest in front of parliament in the capital on Monday.

The roughly half a dozen gunmen who attacked the camp were riding in a car and on motorcycles, said the security officials. They killed six soldiers at the camp and a policeman who tried to intercept them as they were escaping. Three other policemen were wounded, said the officials.

The camp that was attacked was set up to look for the debris of a helicopter that crashed in the area recently, said the officials.