Armed men have kidnapped six engineers working for Iraq's state-owned Northern Oil Company, police said. The six were returning to the oil city of Kirkuk, 250km north of Baghdad, from a meeting at the Baiji refinery, Iraq's biggest, when they were stopped about 30km from Kirkuk, on Friday. No further details were available.Security problems in the Kirkuk area, including frequent attacks on pipelines, have hindered Iraq's ability to exploit the vast potential of the northern oilfields. Nearly all of Iraq's oil exports - averaging below two million barrels a day - have come from the southern fields around Basra.