At least four people have been killed in a suspected suicide attack in north-west Pakistan, amid signs a truce with militants may be breaking down.
The blast in the town of Bannu would be the first suicide attack since March when Pakistan's new government indicated it would talk with militants.
In another attack in the north-west gunmen shot dead two policemen outside a bank in the Swat valley, police said.
Last week top militant Baitullah Mehsud suspended talks with the authorities.
"Pakistan's government must bring the frontier area under its control as quickly as possible"
Mehsud, who called a truce on 24 April, said discussions were on hold because of the government's reluctance to pull out troops from tribal areas.
Attempts in recent years to defeat pro-Taleban forces operating across the Pakistan-Afghanistan border have failed.
Patrol ambushed
Over the past year Pakistan's north-west has seen dozens of suicide attacks, blamed on Islamist militants.
No group has accepted responsibility for the latest blast in Bannu, but militants loyal to Mehsud claim to have carried out similar attacks in the past.
Police say the bomber, who was travelling in a rickshaw, blew himself up near a security checkpoint in the garrison town in North-West Frontier Province.
The rickshaw driver was killed, as were another civilian and a policeman, the authorities said. Four others were wounded.
The bombing comes a day after a security patrol in Baitullah Mehsud's native South Waziristan tribal district came under fire from suspected Taleban fighters. One soldier was injured in the attack.
Mehsud is accused of being behind the assassination of former Prime Minister Benazir Bhutto in December, which he denies.
Although his stronghold is in South Waziristan, his influence extends across territory near the Afghan border.
Dialogue
Pakistan's new government has said it will deal with Islamic militancy through dialogue and development.
Last month the authorities set free Maulana Sufi Mohammad, the founder of an outlawed Islamist group that has fought in Pakistan and Afghanistan.
He was released under an agreement to renounce violence and help restore peace in the north-west valley of Swat.
The valley was a prominent destination for tourists until the cleric's son-in-law, Maulana Fazlullah, led a Taleban-style insurgency last year.
On Tuesday, a group of armed militants opened fire outside a branch of the Habib Bank in Matta Tehsil in Swat district, the official news agency, the Associated Press of Pakistan, reported. Two policemen on guard were killed.
American officials cautiously support the new government's efforts to reach peace through talks.
But they admit they are concerned and say there is a problem enforcing such agreements.
On Monday US Deputy Secretary of State John Negroponte urged Pakistan's new government to act "as quickly as possible".
"We will not be satisfied until all the violent extremism emanating from the [tribal belt] is brought under control," he said.
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