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Militants killed five police officers — including a police commissioner — on Saturday, the second anniversary of the U.S.-led invasion of Iraq, as the insurgency pressed on with its tactic of targeting Iraqi security forces, Shiites (search) and Kurds (search) and focusing less on American troops.

Newly elected Shiite and Kurdish leaders marked the March 19, 2003, start of the war with a fresh promise to form a government by the end of the month, when the National Assembly convenes for only the second time, nearly two months after lawmakers were elected.

Around the world, tens of thousands of anti-war protesters marked the day with street demonstrations, with the largest turnout among residents of America's closest ally in the war — Britain, where 45,000 assembled in London's Hyde Park (search) before marching to the U.S. Embassy (search).

In Waco, Texas, President Bush said "the Iraqi people are taking charge of their own destiny." He issued the order to invade Iraq, declaring Saddam Hussein a threat to the United States and the Middle East because he allegedly had weapons of mass destruction.

Chemical, biological and nuclear weapons never were found, and the administration subsequently said the invasion was still worthwhile because it freed Iraq from Saddam's tyranny and provided a democratic model for the Middle East.

In violence Saturday, gunmen killed Ahmed Ali Kadim, a Baghdad regional police commissioner, as he traveled to his office in the Doura neighborhood. In the oil-rich northern city of Kirkuk, attackers killed a policeman, then bombed his funeral procession, killing three other officers, including the cousin of Jalal Talabani, the Kurdish leader pegged to become Iraq's next president.

A suicide attacker trying to kill U.S. troops in the insurgent stronghold of Ramadi, 70 miles west of Baghdad, prematurely detonated his car bomb, killing only himself, Iraqi police and the U.S military said.

Despite the continuing attacks, the top U.S. general in Iraq, Army Gen. George Casey, said recently that the level of violence against U.S. troops had dropped significantly since the Jan. 30 elections. That appeared to be the result of a tactical shift by the insurgency, made up mostly of Sunni Arabs who were dominant under Saddam, to focus violence on majority Shiites and Kurds, two groups persecuted under the dictator's Baath Party rule.

The Jordanian-born terrorist mastermind Abu Misab al-Zarqawi and his Al-Qaida in Iraq group have said they hope their relentless wave of bombings, kidnappings and beheadings will lead to a sectarian war.

Shiites make up about 60 percent of Iraq's 26 million people, while Sunni Arabs make up about 20 percent of the population. Kurds, who are Sunni but mostly secular, make up 15 to 20 percent.

Sunni Arabs mostly stayed away from the elections, either because they feared reprisals or because they chose to boycott them.

"The terrorists have one policy. They want to prevent the formation of a democratic government and want to draw the people of Iraq into a sectarian war," said Ali al-Faisal, a member of the Shiite clergy-backed United Iraqi Alliance.

"In the past, they were targeting the American forces because they were in charge of security. After the new Iraqi army and police were established, and succeeded in maintaining security and began annihilating them, they shifted their attacks. But they will fail because there is a real intent to fight terrorism," al-Faisal said.

The 275-member National Assembly, Iraq's first democratically elected legislature in recent memory, was first convened Wednesday.

Talabani and the Kurdish coalition agreed last week to form a government with Shiite politician Ibrahim al-Jaafari as prime minister.

An alliance official said differences now had been resolved over a timetable for returning control of Kirkuk to the Kurds once a government is formed, overcoming a major stumbling block. Saddam had conducted ethnic cleansing in the city and region, driving Kurds from their homes and replacing them with Arabs.

"In the next session of parliament, Talabani will be named president and he will officially ask Ibrahim al-Jaafari to form the new government," said Azad Jundiyan, a spokesman for Talabani's Patriotic Union of Kurdistan.

The Kurds and Shiites have repeatedly sought to reach out to the Sunni Arabs, in the hope that their inclusion will help deflate the insurgency, but a number of Sunni groups, including the influential Association of Muslim Scholars, met Saturday and again rejected any participation in the new power structure.