Seven persons were killed and 45 others injured in four separate bomb attacks in Pakistan’s restive northwest on Wednesday, heightening concerns about security for the landmark May 11 general elections.

Three persons were killed when a suicide attacker rammed his explosives-laden car into houses near a police station at Domail in Bannu district of Khyber-Pakhtunkhwa province early in the morning.

The explosion was heard from several kilometres away.

Two women and a policeman were killed while 27 others, including 10 women and children and nine policemen, were injured, police officials said.

Seven houses were destroyed or damaged by the blast.

Some of the critically injured were sent to a military hospital.

A bomb disposal squad official said an estimated 500 kg of explosives were used in the attack.

Two persons were killed by a powerful explosion at a crowded market in Hangu district of Khyber-Pakhtunkhwa province.

According to police, the bomb was planted in a vegetable cart.

About 20 people were injured by the blast and two of them died in hospital.

The target of the attack could not immediately be ascertained.

Two more persons were killed when a bomb went off outside the home of an Awami National Party leader at Khar, the main town of Bajaur tribal region, officials said.

In yet another case of violence, Independent candidate Shahjee Gul escaped an explosion that occurred near his election office in Jamrud area in the lawless Khyber tribal region Wednesday morning.

No loss of life was reported in the attack.

Personnel of the Khasadar Force cordoned off the area and launched a search operation.

No group claimed responsibility for the attacks.

Pakistan has witnessed a sharp surge in violence by the Taliban and other militant groups ahead of the May 11 general elections.