The Public and Commercial Services Union(PCS) members voted last month to take strike action, following an earlier row over protective glass screens at Bridgend.

Benefits Agency staff across the UK are striking

Workers at 1,600 Jobcentre and Benefits Agency offices across the UK have also joined the dispute.

The Department of Works and Pensions has dismissed support for the strike as being "less than enthusiastic".

Officials said more than two-thirds of the 5,500 staff affected by the dispute in Wales had reported for work and were in work delivering a service to the public.

But the department confirmed that six of Wales's 134 Employment Service and Benefit Agency offices will be closed until Friday.

Those affected include Holyhead, Aberdare, Pontypridd, Porth, Port Talbot and Tonypandy.

Offices in Carmarthen, Haverfordwest and Pembroke Dock are also operating a limited service.

Benefit payments made between now and Christmas will not be affected and people making new claims will be dealt with on Friday.

Settlement sought

The PCS said the industrial action was being taken over "very real fears" that its members could be put at risk without adequate protection.

PCS national officer Jeff Evans said the direct course of action was in response to the Bridgend Benefits Agency dispute, when 120 workers started industrial action in October following concerns over safety.

"PCS does not take strike action lightly but management must now acknowledge the strength of feeling among staff and get back into talks," said Mr Evans.

Hostile reaction

The Bridgend workers have received previous support from Janet Davies AM, Bridgend AM Carwyn Jones and Hywel Williams, MP for Caernarfon.

In October, PCS area secretary Richard Bould said staff should not be placed at risk of harm by dealing with customers in an open plan environment.

"Most benefit claimants pose no risk at all to staff, but in the case of a very small minority, there is always the risk of a hostile reaction," said Mr Bould.

He added the Bridgend office had the highest reported number of such incidents in Wales.