A suicide bomber has detonated his explosive-laden vest near a van carrying Japanese car workers, who narrowly escaped injury in Pakistan’s port city of Karachi.

The van had been heading to an industrial area where the five Japanese nationals worked at Pakistan Suzuki Motors, local police chief Arshad Awan said.

He said police escorting the Japanese returned fire after coming under attack, killing an accomplice of the suicide bomber whose remains were found at the scene of the attack.

“All the Japanese who were the target of the attack are safe,” he said.

Three bystanders were injured in the incident.

Pakistan’s President Asif Ali Zardari and Prime Minister Shehbaz Sharif denounced the attack on the Japanese nationals.

In separate statements, they praised police for quickly responding and foiling the attack. They also vowed to eliminate terrorism and prayed for the speedy recovery of those who were injured.

Images on local news channels showed a damaged van, as police officers arrived at the scene of the attack.

Mr Awan said the three passers-by who were wounded in the attack were in stable condition at a hospital.

Police were escorting the van after receiving reports about possible attacks on foreigners who are working in Pakistan on various Chinese-funded and other projects, said Tariq Mastoi, a senior police officer. He said a timely and quick response from the guards and police foiled the attack and both attackers were killed.

No-one immediately claimed responsibility, but suspicion is likely to fall on a small separatist group or the Pakistani Taliban who have stepped up attacks on security forces in recent years.

Insurgents have also targeted Chinese nationals who are working in Pakistan on projects relating to the China-Pakistan Economic Corridor, which includes a multitude of megaprojects such as road construction, power plants and agriculture.