Pakistani police increased security at police stations in Karachi today after gunmen killed five policemen.
Senior government officials said they suspected Islamic extremists were involved in yesterday's attack. A band of 10 to 12 gunmen killed the five policemen and wounded one at a city police station.
"The level of alert has been heightened at all police stations because we do not rule out more such attacks," said Mr Fayyaz Leghari, a deputy inspector-general of police.
The attack, one of the boldest on Karachi police in recent years, might have been in retaliation for an army operation against foreign militants in Pakistan's western tribal areas on the Afghan border, or an attempt to derail the hunt for extremists in Karachi, a security official said.
Police have set up small posts on roof tops and increased security at all of its nearly 100 police stations in an attempt to prevent another assault, police said.