BBC Islamabad Correspondent Owen Bennett-Jones: "Security will be stepped up"

A group of masked gunmen burst into the Imanbargah Hurmain mosque in the eastern Al-Falah district and opened fire with automatic weapons on worshippers during dawn prayers.

In a separate incident, a Shia Muslim has been shot dead by two unknown gunmen in Multan, in Pakistan's Punjab province.

The attacks follow a week of growing violence against the Shia community.

The floor of the mosque was littered with bodies of the slain

Shias have blamed Sunni Muslim extremists for the attacks, in particular the violent Sipah-e-Sahaba (Guardians of the Companions of the Prophet).

Officials say the incidents have taken place after several months of relative calm and indicate that armed gangs may be back on the streets to start another round of sectarian violence.

About 4,000 people have been killed in the last four years in political, ethnic and sectarian violence centred on Karachi.

Pool of blood

There were about 30 worshippers in the mosque when the attack happened, witnesses said.

Correspondents say local residents and volunteers rushed to the mosque and helped the injured as blood spread all over the floor of the prayer room.

Survivors of the attack said the gunmen fled after making sure that most of the people attending the prayers had been hit.

"I just saw two masked men who opened fire at us, and then there was only blood, screams and shouts," said Ghulam Hussain Jafri, the Imam of mosque, who was among the injured.

Sectarian strife

Soon after the incident hundreds of people gathered outside the mosque, chanting slogans against the government and Sunni extremists.

Karachi's security forces have been put on alert

The government condemned the killings and promised additional security throughout the country.

"Evil forces are active to destabilise democratic forces in the country," said Punjab provincial Law Minister Raja Elahi, although he did not indicate to whom he was referring.

In Multan, Akhtar Hussein, said to be a supporter of the main Shia Tehrik-e-Jafria party, was shot dead outside his bakery in the early hours of the morning.

A BBC correspondent says a 10-year-old boy, who was in the shop at the time, was hurt in the attack.

On Thursday, a Shia activist Ejaz Hussain, a lawyer, was killed in Gujranwala town, about 65 km (40 miles) north of Lahore.

On Tuesday a central secretary-general of the Tehrik-e-Jafria party, his daughter and bodyguard were killed in the North West Frontier Province.