LONDON, England (CNN) -- Thousands of Iraqis have been captured or have surrendered to UK authorities, Britain's Chief of Defence staff, Admiral Michael Boyce, said Saturday morning. 

Boyce told a London press conference the men had been taken as prisoners of war. 

The 51st Division of the Iraqi army -- with 8,000 to 10,000 soldiers -- surrendered in the Basra area, in southern Iraq, Boyce added. 

"We have many thousand prisoners of war," he said. 

But later Gen. Tommy Franks, the head of U.S. Central Command, told reporters between only one and two thousand Iraqi troops are in custody.

He added that in addition to the Iraqi troops who have surrendered and have been taken into custody, "thousands more have laid down their weapons and have gone home." 

Pockets of resistance were still present in the Iraqi port city of Umm Qasr on the Al Faw Peninsula Saturday, which had been taken by joint coalition forces the day before, British Army spokesman Col. Chris Vernon said. 

The port was secure, but allied troops continue to come under fire Saturday, he added. 

"I wouldn't call it serious military resistance, but there were small groups of determined men wandering around with weapons and 'RPGs' (rocket propelled grenades)," he said. 

He described the Umm Qasar attack as a "difficult operation" because the U.S.-led coalition had problems distinguishing uniformed and "guys wearing civilian clothes." 

UK Defence Secretary Geoff Hoon also told reporters that most of the oil wells and refineries now under British troop control in southern Iraq had been rigged with explosives and booby-traps. 

Hoon also said that the seven Royal Navy aircrew -- six British and one American -- were still missing after two Sea King helicopters collided over the Persian Gulf early Saturday. He said the crash was not the result of enemy action. Earlier UK Central Command in Qatar said the seven had died. (Full story) 

The accident was the second involving coalition forces in two days. On Friday a U.S. Marine CH-46 helicopter crashed in Kuwait, killing all 12 people aboard.