Car bombs and mortar attacks killed 50 people in Iraq, police and local officials said on Saturday, while the U.S. military said six of its soldiers had been killed in the past two days.

One British soldier was also killed in the south.

The fresh violence follows a lull in Iraq, where tens of thousands of U.S. and Iraqi troops are on the offensive against insurgents in a bid to halt a slide into sectarian civil war.

Rising U.S. casualties have put President George W. Bush under mounting pressure from Democrats and from some senior figures in his own Republican Party to justify his strategy of ordering 28,000 more troops to Iraq.

There are now 157,000 U.S. military personnel there.

A truck bomb ripped through a bustling outdoor market in the northern town of Tuz Khurmato on Saturday, killing 20 people and wounding 90, police said.

Jasim Ali, 30, said he looked frantically for his wife when he heard the explosion.

"I ran to the market and saw burned cars along with dead and wounded people everywhere. I screamed until I found my wife. She was wounded in the head and her hand," said Ali, his clothes stained with his wife's blood.

A suicide car bomber killed 22 people and wounded 17 others when he drove his vehicle into a group of Shi'ite Kurds near Iraq's border with Iran on Friday evening.

Ibrahim al-Bajilam, head of the local council in Garghoush village, said the victims were returning from a funeral. The village is in Diyala province, where U.S. and Iraqi forces last month launched an offensive against Sunni Islamist al Qaeda.

The U.S. military said roadside bombs killed four soldiers in Baghdad, three on Friday and one on Thursday. It said two Marines were killed in combat in Anbar province on Thursday.

One British soldier was killed in the southern city of Basra on Friday in a big operation involving around 1,000 British troops to flush out suspected militants. Three others were wounded in the fighting, the British military said on Saturday.

Overnight, a mortar bomb killed seven members of one family as they slept on their roof in the Sunni neighborhood of Fadhil in central Baghdad, police said. They included a couple and their four children, aged nine to 17.

Electricity blackouts have stopped air conditioners from working, so many Iraqis find it cooler to sleep on roofs.

DEADLY PERIOD

The April-June period was the deadliest three months for U.S. troops since the March 2003 U.S.-led invasion. So far this month, 20 soldiers have been killed, half of them in Baghdad.

As U.S. public opinion hardened towards the war, a senior U.S. military commander warned against cutting troop levels, saying Iraq's security forces could not fight on their own.

"It would be a mess," said Major-General Rick Lynch, commander of U.S. forces in an area stretching from southern Baghdad through a region known as the "Triangle of Death".

He said the extra U.S. troops had given commanders the ability to provide greater security.

"If those surge forces go away, that capability goes away. And the Iraqi security forces aren't ready yet to do that," Lynch told reporters in Washington in a video link-up.

Bush has shown no public sign of changing course over Iraq.

(Additional reporting by Alister Bull, Mussab Al-Khairalla and Waleed Ibrahim in Baghdad and Kristin Roberts in Washington)