(Adds police, Foreign Ministry comment)

PESHAWAR, Pakistan, July 8 (Reuters) - Unidentified gunmen killed three Chinese workers and wounded another on Sunday in what Pakistani officials said was a terrorist attack apparently linked to the bloody siege of militants at an Islamabad mosque.

The four Chinese, who worked for a motorcyle company making three-wheeled auto-rickshaws, were ambushed as they were leaving their factory on the outskirts of the northwestern city of Peshawar, a provincial government official said.

"It's being investigated from different angles, but apparently it looks as if it's linked to Lal Masjid," Peshawar police chief Abdul Majeed Marwat told Reuters.

The siege by security forces of Islamist militants holed up in the Pakistani capital's Lal Masjid, or Red Mosque, has raised fears of a militant backlash. At least 21 people have been killed in the siege since Tuesday.

The Pakistani Foreign Ministry condemned what it described as a terrorist attack on the Chinese. China is Pakistan's most steadfast ally and is involved in numerous development projects.

Last month, radical Islamist students based at Lal Masjid kidnapped six women and a man from China, whom the students said were involved in prostitution.

The seven were released after about 17 hours, but government officials said the kidnapping was a key factor forcing action against the mosque.

Clashes broke out on Tuesday between students and paramilitary troops tightening security outside the mosque compound.

Three Chinese technicians working on a port project in the volatile southwestern province of Baluchistan were killed in a bomb attack in 2004.

The same year, Islamist militants kidnapped two Chinese engineers working on a dam in the South Waziristan region on the Afghan border. One was killed during a rescue operation, while the other was freed. (Additional reporting by Sheree Sardar)

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