Roundup: Australians hold ceremonies to honor their war dead on Anzac Day

Hundreds of thousands of Australians flocked to ceremonies held across the country in honor of those who died in war on Australia's national day of remembrance, Anzac Day, on Tuesday, while Prime Minister Malcolm Turnbull paid a secret visit to Australian troops stationed in Iraq and Afghanistan.

Anzac Day is held on April 25 each year on the anniversary of the first landings of Australian and New Zealand Army Corps (Anzac) troops at Anzac Cove on the Gallipoli Peninsula in 1915. The offensive, undertaken during World War I, was deemed one of the campaign's biggest failures, but is memorable for the mateship and camaraderie shown among allied soldiers.

The downpour of rain failed to deter 50,000 of Canberrans from attending the Dawn Service held at the Australian War Memorial when the dawn broke. The service is to mark the anniversary of the Battle of Gallipoli in Turkey on April 25, 1915, the first major military action fought by Australian and New Zealand forces during World War I.

Some 10,000 people also attended the the National Ceremony held later in the morning when veterans marched in front of the Australian War Memorial. Deputy Prime Minister Barnaby Joyce laid wreath as the representative of Prime Minister Turnbull.

The PM's office published photos from the unannounced visit to social media on Tuesday morning, showing Turnbull meeting with Australian servicemen and women who are both assisting local forces in the fight against Islamic State (IS) and helping local communities rebuild from the war.

The trip was kept a secret in order to protect Turnbull and his party, with the prime minister visiting Iraq on Sunday and Afghanistan on Monday, thanking troops for their commitment to helping in the region.

"At every level, you're helping the forces of Iraq defend themselves and liberate their country from Islamic State," Turnbull told the Australian soldiers during his visit, as reported by a press release by the PM's office.

"We are fighting with the same allies we fought with 100 years ago, but in a different fight and I want to thank you on the eve of Anzac Day for your service."

In Iraq, the Australian prime minister visited Australian special forces soldiers in Baghdad, handing out 15 service medals, while he also spent time at Camp Taji with Australian and New Zealand military personnel.

He briefly met with Iraqi Prime Minister Haider Al-Abadi before jetting to Afghanistan, where he visited Camp Qarga outside capital Kabul, and later met with Afghan President Ashraf Ghani.

In a post to social media on Tuesday, the prime minister thanked Australian servicemen and women all over the world for their commitment to keeping the world, the Middle East in particular, safe.

"It has been an honor to meet the servicemen and women in the Middle East to thank the Anzacs of today for their service. Almost 2,000 Australians are helping to defeat and destroy the terrorists, they are defending freedom here so that we can live in freedom at home," Turnbull posted to social media website Facebook.

Across Australia, services and parades are held in cities and small towns to commemorate the war dead and pay tribute to the servicemen and women.

More than 100,000 people lined the Sydney CBD's streets and waved flags as an estimated 16,000 veterans marched by, despite the warning from the police that there might be terrorist attack on the day.

Security was tight in Sydney where police used water-filled barriers and blocked roads amid concerns about a potential lone-wolf style terrorist attack. Endit