Gunmen storm police headquarters in Pakistan’s Karachi

Gunfire has erupted outside of police headquarters in Pakistan's largest southern city as security forces rushed to stave off what appeared to be a bold attack in the heart of Karachi.

Multiple explosions and continuous firing were heard as armed men attacked a police station on .

Police sealed off traffic on the main road through the city and heavy contingents of security forces, including paramilitary soldiers, had arrived at the scene.

Local media reported that there were between eight and 10 assailants. Murtaza Wahab, a spokesperson for the Sindh provincial government, could not provide details.

There was no immediate word of casualties but city police chief Javed Alam Odho confirmed that an attack was underway and said police and paramilitary troops were responding.

It wasn't clear who was behind the assault on the police headquarters, or how many assailants were involved, the police chief added.

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Odho provided no further details and TV footage showed officers surrounding the city's central police station. Residents said they also heard explosions, but it was unclear what caused the sound of nearby blasts.

Surge in terror attacks

No group has so far claimed the attack.

Pakistan has witnessed a surge in terror attacks since November when Pakistani Taliban, which is designated as terrorist organization, ended a months long cease-fire with the government. 

Pakistan's outlawed Tehrik-e-Taliban are a separate group but are allies of the Taliban in Afghanistan, who seized power there more than a year ago as the US and NATO troops withdrew.

The Taliban takeover in Afghanistan emboldened terrorists in Pakistan's territory, whose top leaders and fighters are hiding across the border.

READ MORE: Three police officers dead after terrorist attack in northwest Pakistan