Violence in Iraq killed 27 people on Tuesday, officials said, as the country's cabinet discussed how to curb unrest that has left over 500 dead this month and raised fears of all-out sectarian conflict.

The latest deaths led the UN envoy to Iraq to urge feuding political leaders to meet and resolve long-running crises that have paralysed the government and been blamed for its inability to halt the bloodshed.

As of Tuesday, 530 people have been killed and more than 1,300 wounded in May -- the deadliest month in at least a year, according to AFP figures based on reports from security and medical sources.

Attacks in Baghdad, including a bomb that exploded on a bus in Sadr City, a Shiite area in the capital's north, killed at least six people and wounded more than 30, officials said.

The United States condemned the "terrorist attacks" and said it was in contact with senior Iraqi leaders "to urge calm and help resolve ongoing political and sectarian tensions."

"The targeting of innocent people in an effort to sow instability and division is reprehensible," added State Department spokesman Patrick Ventrell.

May is the second consecutive month in which more than 400 people have been killed, culminating in a total of almost 1,000 dead in less than two months -- a toll that continued to mount Tuesday.

North of the Iraqi capital, a suicide truck bomber killed four people and wounded eight in Tarmiyah, and three relatives of the deputy head of the Salaheddin provincial council were gunned down near Baiji.

Gunmen also killed two Sahwa anti-Al-Qaeda militiamen and wounded two more near Tikrit, the home city of executed dictator Saddam Hussein, while a third was shot dead in the northern city of Kirkuk.

In Mosul, four police and four gunmen died in clashes, and gunmen also shot dead a tribal sheikh in the northern city.

And a bombing near Mosul killed police intelligence officer Lieutenant Colonel Faris al-Rashidi and wounded three other police, while a suicide bomber driving an explosives-rigged vehicle killed a soldier and wounded two south of the city.

The attacks come a day after a wave of violence, including bombings in Baghdad that mainly targeted Shiite areas, killed 58 people and wounded 187.

As the violence raged, Iraq's cabinet discussed its "security challenges" and ways to address them, later announcing several measures aimed at stemming the bloodletting.

These included "pursuing all kinds of militias," calling for a meeting of political powers, providing unspecified support to security agencies, and warning the media against inciting sectarian strife, said a cabinet statement.

Iraq has suspended the licences of 10 satellite television channels for allegedly inciting sectarianism, although an official from the media regulator said Tuesday some of those channels would have their licences restored "soon".

The authorities have unsuccessfully struggled for years to curb the violence plaguing the country.

United Nations envoy Martin Kobler called on Tuesday for Iraq's politicians to talk to each other and address their differences and the violence.

"It is their responsibility to stop the bloodshed now... to act immediately and to engage in dialogue to resolve the political impasse and not let terrorists benefit from their political differences," he said.

Iraq is faced with various long-running political crises over issues ranging from power-sharing to territorial boundaries, paralysing the government.

There has been a heightened level of violence since the beginning of the year, coinciding with rising discontent among Iraqi Sunnis which erupted into protests in late December.

Members of Iraq's Sunni minority, which ruled the country from its establishment after World War I until Hussein's overthrow by US-led forces in 2003, accuse the Shiite-led government of marginalising and targeting them.

Analysts say government policies that have disenfranchised Sunnis have given militant groups in Iraq room to manoeuvre among disillusioned citizens.

Although violence in Iraq has fallen from its peak at the height of the sectarian conflict in 2006 and 2007, when death tolls could run to well over 1,000 people per month, deadly attacks occur daily.