US-led forces in Iraq have issued new casualty figures confirming that the country has seen the bloodiest period of fighting since Saddam Hussein fell.
The US began its offensive in Falluja last Monday
US Brig Gen Mark Kimmitt said about 70 coalition troops had been killed in Iraq since 1 April, while casualties among insurgents were 10 times as high.
President George W Bush said things had improved after a "tough week" in Iraq.
But US commanders have asked for two more brigades to deal with growing unrest, including a rise in abductions.
Seven Chinese were seized near the flashpoint town of Falluja after entering Iraq from Jordan on Sunday - although unconfirmed reports late on Monday suggested they have now been released.
Reports say two Czech television journalists were also taken hostage north of Baghdad on Monday morning.
The latest kidnappings follow the seizure of three Japanese citizens whose fate remains unknown.
Their captors threatened to kill one of them at 1300 GMT unless Japan withdrew its 550 troops, but the deadline passed without any news.
Two US soldiers and seven US contractors are missing after an attack on their convoy at the weekend, the US military said.
Despite the hostage-taking, a tentative truce between US-led forces and Sunni insurgents in Falluja seems to be holding after more than 24 hours.
Local hospital officials in Falluja say the violence has left more than 600 Iraqis dead, most of them civilians. The US military says almost all the casualties were fighters.
The US military has rejected suggestions that the Falluja offensive amounted to "collective punishment" of civilians as well as insurgents.
"Collective punishment is imposed on the people of Falluja by those terrorists and cowards that hunker down inside mosques, hospitals and schools and use women and children as shields," Gen Kimmitt told a news conference in Baghdad.
He acknowledged that during the past week, attacks on coalition forces had been running at two to three times the average rate.
He said the level had reached 50 to 70 attacks per day.
In other developments:
- Iraqi police reportedly regained control of the central city of Najaf under a deal with militiamen loyal to radical Shia cleric Moqtada Sadr - but the US said it had no knowledge of such a deal
- A Romanian working for a security company was killed and another wounded near Baghdad on Sunday when gunmen opened fire on their convoy, said Romania's ambassador to Iraq
- Three US marines were killed in fighting on Sunday in Anbar province west of Baghdad, a military statement said; at least three US soldiers were killed in separate incidents in Baghdad and Tikrit
President Bush, speaking after talks with Egyptian President Hosni Mubarak, told reporters: "The situation in Iraq has improved. But... it was a tough week, because there was lawlessness and gangs that were trying
to take the law in their own hands."
The ceasefire in Falluja remained "tenuous", because some attacks by insurgents had continued, Lt Gen Ricardo Sanchez told a news conference.
He said talks with local militants on a lasting truce had not gone beyond "initial discussions", adding: "We are not negotiating at this point."
The head of US Central Command in Iraq, Gen John Abizaid, criticised the performance of Iraqi forces in dealing with insurgents in the south, saying a number of Iraqi units did not stand up to what he called the intimidators of the forces of Mr Sadr's militia.
Gen Abizaid said the mission of his forces was to "kill or capture" Mr Sadr and he was seeking two brigades of additional combat troops to tackle the current unrest.
More foreigners seized
It is not clear what the seven Chinese men detained late on Sunday were doing in Iraq.
Chinese sources say they were farmers and fishermen from Fujian province in south-east China and did not work for the government.
Hours after the Chinese authorities appealed for their release, the official Chinese news agency, Xinhua, reported that they had been freed, but gave no further details.
The BBC's Rupert Wingfield-Hayes in Beijing says the abductions make little sense to most Chinese, since
China opposed the US-led war and has no troops in Iraq.
Our correspondent says the abductors may have mistakenly thought the men were Japanese or Korean, two countries that are part of the US-led coalition.
The kidnappings have overshadowed US Vice President Dick Cheney's tour of East Asia, which included a
meeting with Japanese Prime Minister Junichiro Koizumi on Monday.
"We wholeheartedly support the position the prime minister has taken with respect to the question of the Japanese hostages," Mr Cheney told reporters afterwards.
Meanwhile, the deadline given by kidnappers of US civilian Thomas Hamill, who threatened to kill him unless US troops ended the Falluja operation, passed with no indication of his fate.
British civilian Gary Teeley, who was kidnapped in the southern city of Nasiriya a week ago, has been handed over to coalition forces there and is safe and well, the Foreign Office in London said.