Malcolm Turnbull sworn in as Australia's new PM

Turnbull became Australia's 29th prime minister after a surprise ballot of his conservative Liberal Party colleagues voted 54-44 on Monday night to replace Prime Minister Tony Abbott only two years after he was elected. Turnbull's elevation has cemented a culture of disposable leaders as the new norm in Australian politics since the 11-year tenure of Prime Minister John Howard ended in 2007.

"There's been a change of prime minister, but we are a very, very strong government, a very strong country with a great potential and we will realize that potential working very hard together," Turnbull told reporters as he left his Canberra apartment on Tuesday morning.

"I'm filled with optimism and we will be setting out in the weeks ahead ... more of those foundations that will ensure our prosperity in the years ahead," Turnbull added.

Shortly before Turnbull was sworn in, a grim-faced Abbott spoke for the first time since his sudden ouster, warning that the persistent volatility in Australia's government could hurt the nation's standing on the global stage.

"Australia has a role to play in the struggles of the wider world: the cauldron of the Middle East and security in the South China Sea and elsewhere," Abbott told reporters. "I fear that none of this will be helped if the leadership instability that's plagued other countries continues to taint us."

Abbott did not say during his speech whether he will quit politics. He did say he would not destabilize the new prime minister. "There will be no wrecking, no undermining, and no sniping," Abbott told reporters.

Turnbull, a 60-year-old former journalist, lawyer and merchant banker known for his moderate views, was party leader for two years before Abbott ousted him by a single vote in a similar leadership ballot.

The Liberals were elected in 2013 as a stable alternative to the then-Labor government. Labor came to power under Kevin Rudd at elections in 2007, only to dump him for his deputy Julia Gillard in 2010 months ahead of elections. The bitterly divided and chaotic government then dumped Gillard for Rudd just months before the 2013 election.

Successive opinion polls showed that the government was likely to lose in next September's elections under Abbott's leadership. Opinion polls show that Turnbull is more popular than Abbott, but his support for environmental steps against carbon alienated some on the party's right.

Wire services