failure to compile an interrupt handler

Hello,
I am stuck with handling interrupts on lpc3180 uC.I have the following interrupt routine:

void IRQ_Handler (void) __irq  {
        MSTIM_INT = MSTIM_INT | 2;
        PIO_OUTP_SET | = 4;
        MSTIM_CTRL = MSTIM_CTRL | 1;
  }

and the following modifications done to the startup code (PHYTEC_LPC3000.s) :

;IRQ_Handler     B       IRQ_Handler  ;(commented)
      IMPORT                  IRQ_Handler ;(added)

The problem is that the code does not compile, I get the following error description:

PHYTEC_LPC3000.s(666): error: A1163E: Unknown opcode IRQ_Handler , expecting opcode or Macro
PHYTEC_LPC3000.s:   666 00000058 IMPORT     IRQ_Handler                  ; Enable IRQ HANDLER

Could someone please give a hint of what could possibly cause the compilation failure and how should I modify the code so, that it would become acceptable?
Thanks in advance!