The suicide bomb attack that killed 22 people in Lahore today is a bloody reminder that Pakistan is fast becoming the main battlefield of Islamic militants.

The country is already gripped by extreme political tension after the assassination of Benazir Bhutto two weeks ago, and today's atrocity — the latest in a string of attacks on politicians and security officials — will increase concerns about the fate of national elections due on February 18. The poll has already been rescheduled once because of Ms Bhutto's murder.

The bomber blew himself up among police deployed outside the High Court ahead of a planned anti-government protest by lawyers. There was no immediate claim of responsibility, but security officials suspect that militants linked to the Taleban and al-Qaeda could be behind the attack.

Police suspect that the group that masterminded the attack on Ms Bhutto might also be linked to the Lahore bombing.

Scotland Yard investigators are in Lahore today, visiting forensic laboratories to examine evidence connected to Ms Bhutto's murder in the garrison town of Rawalpindi.

She and about 20 others were killed in a gun and suicide bomb attack after she had addressed an election rally. The assassination of Pakistan’s most popular leader and twice prime minister led to widespread violent protests that left dozens more dead and forced a six-week postponement in the elections.

Nisar Memon, the Pakistani Minister for Information, said that today's violence would not affect the election schedule. However, officials fear more violence in the run up to the elections, crucial for Pakistan’s long-awaited return to democracy after nine years of military rule.

There has been a steep rise in terrorist violence since the army stepped up its operations against the Islamic militants seeking to establish Taleban-style conservative Islamic rule in the troubled northern border region.

Military and intelligence agencies have born the brunt of the attacks since last July, when special forces stormed the radical Red Mosque in the capital, Islamabad, killing more than 100 people, including the mosque's leader, a pro al-Qaeda cleric. Many of the dead were poor students from the north.

Security officials have blamed the suicide bombings on Baitullah Mehsud, a pro al-Qaeda militant leader spearheading fighting against government forces in the lawless Waziristan tribal region. He has also been accused of masterminding the attack on Ms Bhutto. The Government has released the names of several prominent figures believed still to be on the terrorist hit list, including Nawaz Sharif and a half a dozen leaders of other political parties.

The prevailing political uncertainty has helped the extremists to expand their influence. The spread of Islamic militancy out of the border areas into Pakistan's heartland has had a frightening and destabilising effect.

In 2007 nearly 1,000 people were killed in suicide bombings, making Pakistan second only to Iraq in the number of such attacks. Most of the victims were from among the military, the former patrons of the jihadis. In the past three months 300 soldiers have been killed in 20 suicide attacks, particularly in the troubled northern areas.

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