LONDON - Sadiq Khan was sworn in as London mayor Saturday after being elected the first Muslim leader of a major Western capital, as the Conservatives defended attempts to link him to extremism during the campaign.

The opposition Labour lawmaker, the son of a Pakistani bus driver, broke from convention by taking his oath of office in a multi-faith ceremony at Southwark Cathedral.

"My name is Sadiq Khan and I'm the mayor of London," the 45-year-old said to cheers from supporters, who had earlier given him a standing ovation as he walked in.

He added: "I'm determined to lead the most transparent, engaged and accessible administration London has ever seen, and to represent every single community, and every single part of our city, as mayor for all Londoners."

Khan won 57 percent of the vote in Thursday's mayoral election, securing 1.3 million votes to see off multimillionaire Conservative Zac Goldsmith and make history as the city's first Muslim mayor.

In his victory speech in the early hours of Saturday morning, Khan had referenced the negative campaign against him by saying London had chosen "unity over division".

Conservative Prime Minister David Cameron had led the attacks against Khan for sharing platforms with radical Muslims at public events, and Goldsmith said he was "radical and divisive".

There was criticism from across the political spectrum on Saturday at the tone of the Tory campaign, but Defence Secretary Michael Fallon insisted it was legitimate.

"Both candidates were asked questions about their backgrounds, their personalities, their judgment, the people they associate with," he told BBC radio. "That's the nature of our democracy and the rough-and-tumble of politics."

News of the win was applauded in Pakistan, with Bilawal Bhutto, leader of the opposition Pakistan People's Party and son of former prime minister Benazir Bhutto, and rival opposition leader Imran Khan tweeting congratulations. New York Mayor Bill de Blasio said he was looking to working with his "fellow affordable-housing advocate" while Paris Mayor Anne Hidalgo tweeted that Khan's "humanity (and) progressivism will benefit Londoners".

Former Conservative government minister Sayeeda Warsi also offered her congratulations "from this daughter of a Pakistani bus driver to the son of a Pakistani bus driver", and condemned her party's campaign.

"Our appalling dog-whistle campaign lost us the election, our reputation and credibility on issues of race and religion," she said. Khan admitted representing some "pretty unsavoury characters" during his previous job as a human rights lawyer but said their views were "abhorrent" and condemned the Conservatives' "desperate" attacks.

Goldsmith's sister Jemima, the ex-wife of Pakistani cricketer and politician Imran Khan, said the tone of her brother's campaign "did not reflect who I know him to be".

Cameron's former adviser, Steve Hilton, said Goldsmith had brought back the "nasty party label".

In the audience at Southwark Cathedral was Doreen Lawrence, an anti-racism campaigner whose teenage son Stephen was killed by a gang of white youths.

"I never imagined in my lifetime I could have a mayor of London from an ethnic minority," she said.

Khan has broken the eight-year hold of the Conservatives on City Hall, succeeding the charismatic Boris Johnson in a prestigious post that has responsibility for transport, housing, policing and promoting economic development.

His success was a boost for Labour leader Jeremy Corbyn, a veteran socialist who has been battling a row over anti-Semitism and growing criticism from the moderate wing of his party since his election in September.

At the Lahore Karahi restaurant in south London, customers and staff celebrated, shouting out in Urdu, "Sadiq Khan Zinda Baad!" (Sadiq Khan well done!)

A favourite haunt of the Khan family, the restaurant in the south London district of Tooting buzzed with excitement.

"We are happy now but he has to fulfil the promises he made," said waiter Shehzad Azhar, 30. "The housing crisis and the transportation come first."

"He will do good things," added fellow employee Malik Ahmed, 32.

Outside Khan's mosque, 50-year-old Asim said: "He is above the polemics. He ran a very clean campaign, very honest, and that's what Londoners liked."

Businessman Shahzad Saddiqui said Khan's background would help him to bring Londoners together. "Sadiq Khan will have a unifying factor because he is Muslim, an immigrant, he is from the working class, so he understands the working-class people and he can associate with them," he said.

"He knows also how the Muslim community is constantly bashed in the media and he will address that."

The latest census showed that 12.4 percent of Londoners are Muslim, 48.4 percent Christian, 1.8 percent Jewish and 20.7 percent have no faith.

The Muslim community is hugely varied, covering multiple ethnic and social backgrounds as well as a variety of moderate and traditionalist views.

In the East End, which has a large Muslim minority, voters said they had cast their ballots for Khan because of his policies rather than his religion.

Fahim Ahmed, a 35-year-old stallholder of Bangladeshi origin selling Islamic dresses at Whitechapel street market, said he was voting for the centre-left Labour party as much as for the individual.

But he welcomed the election of a candidate whose parents emigrated from Pakistan to Britain in the 1960s, saying: "He's from our culture."

At a nearby stall, Sabiha Choudhary was shopping for vegetables dressed in a black robe and green headscarf.

"It will not help only the Muslims, it will make a difference for all communities," she said. "Things will be better for people with not much money like us."