A suicide bomber has targeted a security checkpoint in northwestern Pakistan, killing two soldiers, a policeman and a civilian, security officials said.

Wednesday's attack was the second incident to hit Pakistan in as many days.

The bombing happened in North Waziristan, a district in Khyber Pakhtunkhwa province that borders Afghanistan and is a former stronghold of the armed Pakistani Taliban group, also known as Tehrik-i-Taliban Pakistanor TTP.

A number of civilians were also wounded in the attack, according to Rehmat Khan, a local police official.

No one claimed responsibility for the attack but suspicion is likely to fall on the Pakistani Taliban.

In the last six months, the TTP has stepped up its attacks since it unilaterally ended a cease-fire with the Pakistani government, brokered by neighbouring Afghanistan last year.

Also Wednesday, the TTP claimed responsibility for an attack the previous day on an oil and gas plant in Hangu, a district in Khyber Pakhtunkhwa, on the border with Afghanistan.

Four security troops and two private guards were killed in the attack on the facility run by a multinational European company, MOL Pakistan Oil and Gas.

Pakistan has seen an increase in attacks since the Afghan Taliban returned to power in 2021, with TTP, carrying out attacks mostly targeting security forces.

The TTP was formed in 2007 by fighters who splintered off from the Afghan Taliban to focus their fight on Islamabad.

Since the Taliban returned to Kabul, Islamabad has said TTP is using Afghan soil to plot their attacks in Pakistan.

On Monday, officials said two empty girls' schools in North Waziristan were also attacked overnight by terrorists, leaving nine classrooms destroyed but no casualties. The attack has not been claimed by any group.