About 1.5m public sector staff have taken part in the UK-wide strike

Public Service Reform Minister Tom McCabe said he was "disappointed" by the action taken by workers over proposed changes to pension rights.

Schools across Scotland have closed and transport has also been affected.

In a letter to Mr McCabe, unions called for the rights of public sector workers to retire aged 60 to be retained.

Five unions are taking part in the action: Unison, the Transport and General Workers, GMB, Amicus and the National Union of Journalists.

Unison estimated that 152,000 workers took part in Tuesday's day of action in Scotland.

They are angry at plans to scrap a rule which allows public sector workers to retire on a full pension at 60.

I think the government always understood our concerns, I think they maybe didn't understand the strength of feeling that there was Matt Smith Unison In pictures: Protest in Scotland

Employees face having to work until they are 65 or take one third less pension.

The letter from trade unions in Scotland stated: "This can only be described as an incredibly unusual industrial dispute in that ourselves and the employers are in agreement that retaining the existing arrangements are neither discriminatory nor unaffordable."

It also called on the executive to retain the original conditions of the pension scheme that public sector workers joined.

Mr McCabe said the Scottish Executive had no option but to bring in the changes as a result of a European directive.

He told BBC's Good Morning Scotland: "We're talking about a directive that doesn't come into force until October 2006.

Regional round-up of the strike

"So I think it's disappointing to say the least that so many people are losing money and a great many people have been inconvenienced today six months away from this.

"The difficulty here is that there are very few people in local government who qualify for this benefit and even less who have taken it up."

The industrial action has caused disruption across the country.

At least 569 schools in Glasgow, Edinburgh, Aberdeen, Dundee and Inverness have closed their doors for the day.

Although teachers were not striking, schools were affected due to the non-attendance of essential staff such as janitors and school cooks.

The capital's council-run Lothian Buses service was also stopped, and delays were expected for motorists on the Forth Road Bridge due to a shortage of traffic managers.

Unison's Scottish secretary Matt Smith said subsequent days of action were being discussed by the unions involved.