Pakistan was on high alert on Sunday as Shiites prepared to observe the Muslim festival of Ashura, a day after security officials said they had foiled plots aimed at causing massive loss of life.
This year's commemorations come amid widespread militancy and unrest across Pakistan, which on Saturday saw the arrest of Sunni extremists intent on targeting worshippers, security officials said.
Ceremonies for Ashura, which marks the death of the Prophet Mohammed's grandson in the seventh century, were set to take place across the country in an annual event often hit by sectarian violence.
President Pervez Musharraf, in a special message for the holiday, appealed for peace and harmony.
"We have to adopt the great teachings of Islam by rising above sectarian, regional and petty differences. We also have to strengthen peace, harmony and brotherhood in the society," Musharraf said.
Security officials said there were plans to use suicide bombs and cyanide poisoning to kill Shiites celebrating Ashura across the nation.
Police on Friday arrested a teenager who was allegedly part of a five-man squad in the plot to kill opposition leader Benazir Bhutto last month, and who they said had been planning an attack during Sunday's commemorations.
The suspect, 15-year-old Aitezaz Shah, was arrested in the northwestern city of Dera Ismail Khan on Friday, security officials said on condition of anonymity.
Shah told interrogators he had been part of a back-up team of three bombers tasked with killing two-time former premier Bhutto if the original December 27 attack by two men had failed, the officials said.
Interior Minister Hamid Nawaz did not confirm the arrest.
"Security is quite tight and we hope that, God willing, this day passes peacefully," he said.
A second would-be suicide bomber was among five heavily armed militants, all belonging to Sunni extremist groups, seized in Karachi who also planned to use cyanide powder to poison water during the ceremonies.
They were planning to launch an attack Sunday on the Ashura festival in the southern port city, provincial police chief Azhar Farooqi said.
"The aim was to cause widespread human losses," Farooqi said of the plot, in which three others were detained in the nearby city of Hyderabad.
Police recovered six kilogrammes of explosives to be placed in the suicide bomber's jacket, three hand grenades, six detonators, two pistols and two kilogrammes of pellets, Farooqi said.
His officers also recovered 500 grammes of cyanide, which the extremists had planned to mix with the water distributed at kiosks established specially during Ashura.
The group's leader, Mohammad Ejaz from Pakistani Kashmir, belonged to the outlawed Harkatul Jihad-e-Islami, while others were members of banned militant outfits Harkatul Mujahideen and Jaish-e-Mohammad, Farooqi said.
A gun and suicide attack on a Shiite mosque on Thursday killed 10 people.
Pakistani security officials said they believed militants from a Sunni extremist group linked to Al-Qaeda were behind the attack.
Meanwhile, gunmen shot dead an intelligence bureau official near his home in northwestern Seerikh village when he was returning home after offering early morning prayers, police said. (AFP)
Pakistan on alert for religious holiday