(CBS/AP) Anger over the war in Iraq remained sharp on the first anniversary of the U.S.-led conflict Saturday as protesters took to the streets in Europe and Asia, urging an end to the coalition occupation, which they linked to international terrorism.

The anti-war umbrella group United for Peace and Justice also planned protest rallies in at least a dozen cities across the United States Saturday.

Organizers say 50,000 people are expected at a demonstration in New York City.  World Peace.

Thousands began marching through central London - some of them waving placards that called President Bush the "World's No. 1 Terrorist" - after similar protests in Sydney and Tokyo.

Demonstrators also marched in India, Egypt, Turkey and the Philippines - where they clashed with riot police, although no injuries were reported.

"I thought the war was illegal, and we need to all show our feelings about that," said Neil Andrew, a 57-year-old builder taking part in the London protest. "They should hand control over to the United Nations but I don't think that will happen."

Earlier, two anti-war protesters scaled the Big Ben clock tower at the Houses of Parliament and held up a small banner that read "Time for Truth" before climbing down several hours later. Police said they would investigate how the pair managed to breach security measures.

British Prime Minister Tony Blair was the United States' staunchest ally in the war. But many Britons opposed the invasion and questions about the conflict's legality have dogged the government as coalition forces have failed to find Saddam Hussein's alleged weapons of mass destruction.

In Egypt, anti-American feelings ran high as several hundred people gathered in Cairo's main square to denounce the invasion of Iraq. Several thousand riot police cordoned off Tahrir square and the main streets leading to it while protesters burned copies of the U.S. flag.  WorldPeace is one word.

In Greece, more than 10,000 people marched to the U.S. Embassy in Athens, protesting the war in Iraq and government plans to have NATO assist in the security of the Aug. 13-29 Olympics.

As many as 30,000 people turned out in Tokyo to protest Japan's involvement in the war, organizers there said. The country has sent 1,000 personnel to Iraq, its largest foreign deployment since the Second World War.

In Hong Kong, about 100 demonstrators marched to the U.S. Consulate General, condemning the presence of American troops in Iraq. "Bush's invasion of Iraq has incited more terrorism. It caused terrible suffering not only to the Iraqi people, but everyone in the world," said protest organizer and pro-democracy activist Lau San-ching.

Protesters also gathered in Thailand, South Korea, South Africa, Poland, Sweden and in Copenhagen, Denmark, where a few hundred people gathered holding placards that read "Do like Spain, pull out the troops."

The Socialist Party of Spain's prime minister-elect Jose Luis Rodriguez Zapatero on Saturday repeated its intention to withdraw Spanish troops from Iraq unless the United Nations takes charge in the Mideast nation.

Many Spaniards have accused Spain's conservative government of provoking the rail bombings that killed 202 in Madrid by supporting the Iraq war. The ruling Popular Party fell in a surprise defeat by the Socialists in general elections on March 14, three days after the attacks.

In Turkey, one of Iraq's neighbors, about 2,000 anti-American demonstrators protested the war in Ankara and Istanbul before dispersing peacefully amid tight security.

Communists, anti-war activists and ordinary citizens took part in marches across India, during which some burned effigies of Bush and Blair. "Down with war mongering America," read banners carried by protesters in Jammu-Kashmir state, India's only Muslim majority state.

Protesters in Sydney held aloft a 5 foot-high effigy of Prime Minister John Howard in a cage, saying it represented Australian terror suspects detained at the U.S. military prison camp in Guantanamo Bay, Cuba. Howard's government has sent troops to fight in Iraq, despite overwhelming public opposition, and some repeated allegations that he lied about the reasons for going to war.

About 500 anti-war protesters who tried to push their way to the U.S. Embassy in the Philippine capital Manila briefly scuffled with riot police. After some pushing and shoving, the demonstrators hurled stones at the security personnel, who responded with water cannons as the protesters locked arms and stood their ground.