PESHAWAR, Pakistan (AP) — A roadside bomb killed at least five people and wounded several on Monday in a northwestern Pakistani tribal region close to the Afghan border, a government official said.

The bomb was detonated by remote control in Tirah Valley in the Khyber tribal region as volunteers from a government-backed militia were moving into the area, according to the official, Mohammad Iqbal Khan. The attack took place in a remote area of the valley, he said. The wounded were transported to a hospital in the region.

No group immediately claimed the bombing. Islamic militants have been responsible for such attacks. Local and foreign militants affiliated with al-Qaida and the Islamic State group operate on both sides of the long and porous border between Pakistan and Afghanistan. Pakistan's army has been battling the militants in the tribal regions.

The two neighboring countries have long accused each other of not taking action against militants and their safe havens on their respective sides of the border.

U.S. Ambassador to Islamabad David Hale met Pakistan's army chief Gen. Qamar Javed Bajwa on Monday, a U.S. Embassy statement said.

Hale noted President Donald Trump's call for unity in conquering extremism and terrorism that the U.S. leader made at the Arab-Islamic-American Summit in Saudi Arabia, the statement said. He affirmed Pakistan's role and great sacrifices in this effort, it said.

Bajwa assured Hale that Pakistan wouldn't allow its territory to be used for planning or conducting attacks against Afghanistan, the statement said.