Pakistani security forces on Friday killed three gunmen who attempted to storm the compound of the Chinese consulate in the southern city of Karachi.

The attackers, wearing suicide vests and armed with hand grenades and automatic rifles, tried to storm their way into the strongly fortified compound, said Karachi police chief Ameer Sheikh.

One blew himself up outside the compound, killing two police officers and a private security guard, Sheikh said.

Two gunmen were shot dead by security forces in front of the consulate's visa section, which was located outside the main compound, Foreign Minister Shah Mehmood Qureshi told media in the capital Islamabad.

China's Ministry of Foreign Affairs "strongly condemned" the attack, urging the "Pakistani side to take practical measures to protect the security of the Chinese institutions in Pakistan."

Nobody from the consulate was hurt and all 21 Chinese employees were moved to a safer location, Qureshi added.

The minister called the attack a "cowardly attempt to sabotage Pakistan-China relations" and said that such attempts would fail.

Responsibility for the attack was claimed by the Baloch Liberation Army (BLA), a nationalist rebel group opposed to Chinese investment in the south-western province of Balochistan.

The group, which unlike Islamist militants has not carried out suicide attacks until recently, issued a photograph of the three attackers.

Chinese nationals and Chinese infrastructure projects in Pakistan often come under attack by Islamist and nationalist militants opposed to the schemes.

China is building a 62-billion-dollar trade corridor through Pakistan to reach Middle East, Africa and Europe.

Earlier this year, a BLA militant blew himself up inside a vehicle carrying Chinese engineers in Balochistan, injuring several of them.