President Asif Ali Zardari spoke for first time since spending eight days in hospital for a "mild" stroke [Reuters]

Pakistani President Asif Ali Zardari defended his rule and urged the nation to foil "conspiracies against democracy" on the anniversary of his wife Benazir Bhutto's murder.

Zardari addressed at least 300,000 mourners on Tuesday at the Bhutto mausoleum in his first public speech since being treated in hospital in Dubai.

"Today we pay tributes to her," Zardari said in a statement issued by his office. "The best way to do it is to defend and protect democracy and democratic institutions in the country and foil all conspiracies against it."

Benazir Bhutto, who was twice elected prime minister, was killed in a gun and suicide attack on December 27, 2007, in the garrison city of Rawalpindi after addressing an election rally.

No one has been convicted of her killing. Police said people gathered at Bhutto's mausoleum to pay their respects demanded that her killers be arrested.

"We want revenge. Arrest Benazir's killers," the mourners chanted, carrying party flags and photographs of Bhutto, eulogising her and her father Zulfikar Ali Bhutto, who was executed under military rule.

Around 6,000 policemen, hundreds of paramilitary officers, electronic  gates, aerial surveillance and canine units were deployed to ensure security, police said.

Plot rumoured

The ruling Pakistan People's Party (PPP) commemoration of the fourth Bhutto anniversary also comes amidst rising tensions and just two days after political newcomer and national sporting hero, Imran Khan attracted large crowds in Karachi, the country's biggest city.

Tensions have soared between the army and government over a memo allegedly written by one of Zardari's aides that asked for United States intervention to stave off a feared military coup.

General Ashfaq Kayani, Pakistan's army chief, last week denied rumours that his military was plotting to overthrow the government.

Yousuf Raza Gilani, the prime minister, subsequently denied rumours that he wanted to sack Kayani or Pakistan intelligence agency spymaster general Ahmad Shuja Pasha.

Kayani and Pasha have backed calls for an investigation into the memo, sent on May 10 and offering to overhaul the security leadership in exchange for American help to reign in the military after the killing of Osama bin Laden.

Zardari's health

Zardari health has also been under the spotlight following eight days in hospital this month for an illness which has not been publicly disclosed and aides likened to a mini stroke with no lasting effects.

Zardari tackled speculation about his health, saying that he was "not medically out".

Bhutto's son, Bilawal, is co-chairman with his father of the PPP and appealed for democracy to prevail in an editorial written in the English-language Express Tribune newspaper.

He also referred to recent US air strikes that killed 24 Pakistani soldiers on November 26.

"It is only under a democratic government that Pakistan finally stood up to demand respect from the US and to do what the dictator with all his military might could not, evacuate the Shamsi airbase," wrote Bilawal.

The US was ordered to leave the airbase, widely believed to have been a hub for a now-stalled drone war on Islamist militants, this month as part of Pakistan's retaliation for air strikes.

Source: Agencies