BAGHDAD (Reuters) - At least seven civilians were killed in two separate bomb and gun attacks in Iraq on Thursday, doubling the death toll in a bloody 24 hours as U.S. forces prepared to mark the first anniversary of their invasion.

A British military spokesman in Basra said four Iraqis were killed in an explosion outside the southern city's Mirbad Hotel. A child was one of at least two people wounded, witnesses said.

The Basra attack came less than a day after a suicide car bomber killed seven people, including a British engineer, at a hotel in Baghdad on Wednesday evening. U.S. officials blamed that attack on Muslim militants with links to al Qaeda.

Three local employees of a U.S.-funded television station were shot dead at Baquba, northeast of the capital, and two civilians were killed in fighting in another restive town, Falluja. On Wednesday, two U.S. soldiers were also killed.

Security forces have been on alert for an increase in violence ahead of Saturday's anniversary of the U.S.-led invasion on March 20 last year which toppled Saddam Hussein.

Basra, in the Shi'ite Muslim south, long oppressed under Saddam Hussein, has seen fewer attacks than Baghdad and Sunni areas like Falluja and Baquba near the capital. The hotel had been regularly used for news briefings by the British military and by the civilian administration of Iraq's second city.

A British military spokesman said it was not clear whether a car bomb or explosives planted in the street caused the blast.

Locals said an angry crowd had beaten to death a man suspected of being behind the attack. The British military said it was aware of the reports but could not confirm them.

AL QAEDA SUSPECTED

In Baquba, northeast of Baghdad, gunmen opened fire on a minibus carrying local employees of a U.S.-funded television station, killing three and wounding at least five, company officials said. Guerrillas have mounted repeated attacks on Iraqis seen as cooperating with occupying forces.

In Baghdad, rescuers said there were no more survivors in the rubble of the central neighborhood devastated by Wednesday night's suspected suicide bombing, which tore through the Mount Lebanon hotel and neighboring residential buildings.

The U.S. army said it bore the marks of the Ansar al-Islam militant group or of Abu Musab al-Zarqawi, a Jordanian accused by Washington of working for al Qaeda to sow chaos in Iraq.

Rescuers, some using bare hands, worked into the early hours trying to find people trapped under the smoldering ruins. Locals helped carry away bodies torn apart by the blast.

A senior U.S. officers ended hours of confusion in which the death toll was given as high as 27 by saying seven civilians had been killed in the hotel. Officials in London named the dead Briton as telecommunications engineer Scott Mounce. He was 29.

In Baghdad, U.S. Brigadier General Mark Kimmit said that the fact that the explosion was in the middle of the road suggested the Mount Lebanon might not have been the intended target.

By first light, smoke was still rising from a smoldering house, its front wall ripped off in the explosion. On the upper storey, a picture still hung on the wall, a mattress and carpet lying on the floor of what used to be someone's bedroom.

SOLDIERS KILLED

Two U.S. soldiers were also killed on Wednesday in separate mortar attacks by guerrillas, the U.S. army said.

Mortar fire at a U.S. base near Baghdad killed one soldier and wounded seven on Wednesday afternoon, and in the evening a mortar attack on Qusayba on the Syrian border killed a Marine and wounded three, the military said.

The attacks brought to 391 the number of U.S. troops killed in action since the start of the war a year ago.

In the flashpoint town of Falluja, west of Baghdad, guerrillas with rocket-propelled grenades exchanged fire with U.S. troops. An Iraqi man and a child were shot dead. The U.S. military had no immediate information on any U.S. casualties.

The Baghdad car bomb attack marred a White House campaign ahead of the anniversary of the invasion of Iraq to stress the progress made in the year since the war began.

"We will meet this test with strength and resolve. Democracy is taking root in Iraq and there is no turning back," White House spokesman Scott McClellan said.

"This is a time of testing. We will continue to stay to finish the job for the Iraqi people."