Islamabad/Karachi, May 11 (PTI): Tens of thousands voted today in Pakistan's landmark general elections to choose new national and provincial assemblies despite a string of bomb attacks in Karachi and the country's restive northwest that killed at least 15 people and injured many others.

Long queues were seen outside thousands of polling stations across the country despite threats of attacks by the Taliban, which said it would target the elections as they are part of the "infidel system" of democracy.

The polls marked the first democratic transition of power in Pakistan's 66-year history. "The turnout has been amazing it is beyond our expectations," Chief election commissioner Fakhruddin G Ebrahim told PTI after visiting several polling stations.

"There should be a turnout of around 70 to 75 percent by the way the people have responded to these elections," he said.

Thirteen people were killed and over 40 others injured in three bomb attacks in the southern port city of Karachi.

The first blast went off near the election office of Amanullah Mehsud, an Awami National Party candidate contesting polls to the Sindh Assembly.

Mehsud escaped unhurt though several ANP workers were among the dead and injured.

The second blast went off minutes later near a polling station and an ANP office in the same area as rescue teams were busy rushing the victims of the first attack to hospital.

The second blast triggered a stampede at the polling station and disrupted voting.

Two persons were killed and several injured when a bus was targeted by the third blast at Qasba Colony in Karachi.

Two policemen were killed and four others injured in an explosion at Toorghar in Peshawar. In Peshawar, a bomb attached to a motorcycle went off outside a women's polling station, injuring eight persons.

Five persons were wounded when a suicide bomber detonated his explosive vest after he was intercepted by police outside another polling station in a suburb of Peshawar.

Several persons were injured in a blast in Quetta, the capital of the restive southwestern province of Balochistan.

No group claimed responsibility for the attacks.There were also reports of clashes between supporters of rival political parties in parts of Punjab and Sindh provinces.

Women were barred from voting in the lawless North Waziristan tribal region, a stronghold of Taliban and al-Qaeda elements, and parts of Upper Dir and Swat districts of Khyber-Pakhtunkhwa provinces. Announcements were made on loudspeakers of mosques early this morning that no woman would be allowed to vote, said residents of Miranshah, the main town of North Waziristan.

Pamphlets distributed in Miranshah earlier this week warned tribesmen not to let women vote. Reports from Dir said leaders of political parties had reached an agreement that women would not be allowed to vote. The turnout in Islamabad and Lahore was especially strong, with voters standing in queues for hours to exercise their franchise.

"I have never seen such a turnout in Lahore, especially among the women and youths. This seems to be the impact of the campaigning by Imran Khan," said Muhammad Shafeeq, a Lahore resident.

An analyst, who did not want to be named, said Khan's Pakistan Tehrik-e-Insaf party would benefit the most from the large turnout in Punjab, which has more than half of the 272 parliamentary seats for which polls are being held. Former premier Raja Pervez Ashraf, PML-N chief Nawaz Sharif, army chief Gen Ashfaq Parvez Kayani and Chief Election Commissioner Fakhruddin G Ebrahim were among those voted shortly after polling began at 8 am.

Footage on television showed Kayani walking into a polling station in Rawalpindi to vote. The polling followed a bloody campaign marred by Taliban violence. Over 100 people, including candidates, were killed in gun and bomb attacks by the Taliban and other militant groups during the campaign period.

Threats and attacks by the banned Tehrik-e-Taliban Pakistan forced three major parties – Pakistan Peoples Party, Awami National Party and Muttahida Qaumi Movement – to dramatically curtail their campaign. There was no official figure for today's turnout though Election Commission Secretary Ishtiaq Ahmad Khan said it was expected to be more than 60 per cent.

Pakistan's right-wing Jamaat-e-Islami party has decided to boycott the polls, claiming massive rigging and mismanagement at several polling stations.

Jamat-e-Islami (JI) decided to withdraw candidates from Karachi and Hyderabad. The party has called a peaceful strike on May 13 to protest poll rigging. Meanwhile, the MQM also claimed there was rigging and mismanagement at several polling stations in Karachi.

"We fear that around 119 polling stations in some very sensitive areas have been affected. We fear there is wide scale rigging going on in these polling stations to kill the mandate of the MQM in Karachi," senior leader Dr Farooq Sattar told reporters.

Heavy turnout of voters was also seen even in those parts of Karachi where the Tehreek-e-Taliban have considerable presence and influence. Elections in Pakistan have traditionally registered low turnouts and only 44 per cent of the electorate voted in the last polls in 2008.

The turnout for the polls was good in most areas with not only the youth but women, senior citizens and men coming out in large numbers at several polling stations. "Honestly I have never seen the people of these posh areas turn out in such large numbers to vote in the elections. It is clear that the youth and people have responded to the slogan of 'Naya Pakistan'," well known writer Anwar Maqsood said.

A supporter of Imran Khan said, "He (Imran) is the only person who can give us a new Pakistan and he has evoked the enthusiasm of the youth."

There are 86.2 million registered voters while 4,670 candidates are running for parliamentary seats and nearly 11,000 candidates for the four provincial assemblies.

Polling will continue till 5 pm and provisional results are expected to come in by early tomorrow.

Tens of thousands of security personnel, including 70,000 soldiers, have been deployed across the country to maintain law and order during the polls.

The PML-N led by former premier Nawaz Sharif is widely tipped to emerge the single largest party while a spirited campaign by cricketer-turned-politician Imran Khan helped his Pakistan Tehrik-e-Insaf make inroads in the most populous province of Punjab and in urban areas.

The outgoing government led by the PPP was the first one in Pakistan's history to complete its full term of five years.

In the past, governments have been ousted by the army, which has ruled Pakistan for more than half of its history.