Militants attacked the US consulate in the Pakistani city of Peshawar on Monday but were held off by security forces hours after a suicide bomber killed 38 people elsewhere in the northwest.

The attacks underscore the danger posed by militants in nuclear-armed US ally Pakistan after a year of military offensives which have dealt the Islamists significant setbacks.

The assault on the tightly guarded consulate came hours after a bomb blast at a gathering of supporters of an ethnic Pashtun-based political party staunchly opposed to the militants.

"I saw attackers in two vehicles. Some of them carried rocket-propelled grenades. They first opened fire at security personnel at the post near the consulate and then blasts went off," city resident Siraj Afridi told Reuters.

A Pakistani intelligence official said no one was wounded inside the US complex but three of its guards had been killed.

"It was a well-planned attack. It was a suicide attack but no one was hurt inside the consulate," said the official. The US Embassy confirmed it was an attack on their consulate but declined to give any other details.