PESHAWAR, Pakistan - Around 100 militants attacked an important security checkpoint near the Pakistani city of Peshawar early Wednesday, sparking a three-hour clash that killed two police officers and 15 insurgents, police said.

The attack on the Sangu Mera checkpoint comes amid Taliban threats to avenge the May 2 US raid that killed Osama bin Laden elsewhere in Pakistan's volatile northwest. But it is more likely tied to the Pakistani military's offensives against militant groups in its tribal belt bordering Afghanistan.

Sangu Mera lies just along the border of Khyber tribal region, one of the areas where Taliban and other militants have hideouts and where the Pakistani army has staged multiple operations. The checkpoint is about 6 miles (10 kilometers) away from Peshawar, a strategically important city along the way to Afghanistan.

Senior police official Liaquat Ali Khan said the militants bore rocket-propelled grenades and other weapons when they attacked the security forces overnight. But eventually the insurgents were pushed back.

Security checkpoints are frequently attacked by militants in Pakistan - sometimes through suicide bombings and other times involving large numbers of insurgents such as Wednesday's incident. The clashes are often linked to ongoing military offensives in the tribal belt.

Pakistan's army has carried out anti-insurgent operations in six of its seven tribal districts. The one place it has not mounted an offensive is the place the US wants it to most - North Waziristan, a tribal area home to militants whose primary focus is attacking US and NATO troops in Afghanistan.

The Pakistanis say they are too stretched battling insurgents who have attacked the Pakistani state to order a North Waziristan offensive right now. The US relies heavily on missile strikes to take out targets in North Waziristan.

Pakistan and the US are struggling to improve their relations since the Navy SEALs raid that killed the al-Qaida chief in Abbottabad, a northwest garrison city a few hours away from Peshawar.

Pakistani officials consider the surprise raid a violation of their sovereignty, and deny knowing bin Laden was staying in Abbottabad. The US says the secrecy surrounding the mission was vital to its success.