Officials say a suicide bomber and a group of militants have attacked a police station and a security convoy hour apart in restive northwest Pakistan, killing at least three police officers and wounding 20 others

PESHAWAR, Pakistan — Militants ambushed a security convoy and hours later a suicide bomber struck a police station in twin attacks in northwest Pakistan Wednesday that officials said left least three police officers dead and 20 wounded, in the latest sign that violence is escalating in the region bordering Afghanistan.

The first attack occurred in the district of Upper Dir in Khyber Pakhtunkhwa province, where militants ambushed a security convoy, killing three police officers and wounding 15 others, local police official Ibrahim Khan said.

He said security forces returned fire and the exchange was ongoing.

Khan did not immediately say whether any militants had been killed or wounded.

Hours later, a suicide bomber rammed an explosives-laden vehicle into a police station in the city of Bannu, also in Khyber Pakhtunkhwa, wounding at least five police officers, police said. The blast damaged part of the station, but no fatalities were immediately reported.

No group immediately claimed responsibility for either attack, but suspicion is likely to fall on the Pakistani Taliban, known as Tehrik-e-Taliban Pakistan, or TTP.

The TTP is separate from but closely allied with Afghanistan’s Taliban. Pakistan has accused the group of operating from sanctuaries inside Afghanistan, a charge both the TTP and the Taliban-led government in Kabul deny.