The killing of worshippers at a Shi'ite mosque in Pakistan's Punjab province has again focused attention on the turbulent religious climate in Pakistan.

Mazhar Zaidi of the BBC's Urdu Service: "The government has not been able to do anything"

Last year scores of people died in clashes between militant Shia and Sunni Muslims.

And, while extremist groups remain in the minority, there are fears that the government's proposed introduction of Islamic law - the Sharia - could fuel a rise in Islamic militancy.

Pakistan's religious climate is the most volatile it has been since General Zia-ul-Haq came to power in 1981 with a programme of Islamisation.

Some are predicting a backlash to Mr Sharif's Sharia campaign

He declared Islamic law as interpreted by Sunni scholars for the majority Sunni population - and Shia Muslims marched in protest. Many of today's militant sects were born in that era.

Now, with Prime Minister Nawaz Sharif claiming inspiration from the extremist Taleban in Afghanistan for his moves to enforce Islamic law, Shias, like other religious minorities and secularists, are mounting protests.

But there is no proof that the sporadic violence between militant Sunnis and Shias - concentrated mainly in Punjab - has increased because of the Sharia bill. On the other hand, alignments of Sunni extremists are emerging to support the president's Islamisation campaign.

Pandora's box

Recently a mass rally was held in Islamabad and death threats were issued against senators opposing the bill.

While such extremist groups remain marginal, there are fears that Mr Sharif has opened a Pandora's box of religious extremism.

Many regard his Sharia campaign as an opportunistic attempt to gain Islamic votes and dilute the opposition in the face of political crisis.