BAGHDAD — Fifty people were killed on Monday as suicide bombers attacked a political rally and Iraqi police and soldiers cast their votes early for a national election in two days' time, authorities and witnesses said.

A suicide attacker killed at least 30 people and wounded 50 others at a Kurdish political gathering in the town of Khanaqin, 140 km (100 miles) northeast of Baghdad, security sources said.

The Kurds were celebrating the television appearance of Iraqi President Jalal Talabani, a Kurd incapacitated since late 2012, who cast his vote in Germany where he was undergoing medical treatment.

"The attacker snuck among the crowds near the Patriotic Union of Kurdistan's headquarters and blew himself up, causing a tragic massacre," one police officer said, sobbing after he discovered his brother was among those killed.

Meanwhile, Sunni militants, mostly disguised in army and police uniforms, struck at polling centers around Baghdad and northern Iraq as militants tried to disrupt Iraq's fourth national election since the fall of Saddam Hussein in 2003.

A curfew begins on Tuesday night as ordinary Iraqis prepare to vote on Wednesday. Security forces are at war with an al-Qaeda offshoot, the Islamic State of Iraq and the Levant, in western Anbar province and other areas encircling the capital.

Prime Minister Nuri al-Maliki is battling for a third term in office but faces fierce opposition from political opponents, with sectarian violence in the Shi'ite Muslim-majority country at its most intense since 2008.

In the western Mansour district of Baghdad, six police died and 16 others were wounded when a suicide bomber dressed as a policeman detonated his explosives at the entrance of a school being used for voting, police and medical sources said.