Journalists at the Daily Record and Sunday Mail have walked out in a strike over job cuts.
Members of the National Union of Journalists (NUJ) began their 24-hour action at midnight on Friday.
Owner Trinity Mirror wants to shed 70 jobs after merging production of the two titles.
The union voted overwhelmingly last month for two strike days, with the second stoppage planned for Friday 10 April.
Trinity Mirror said it was confident the strike would not stop production of the newspapers.
The company announced proposals in February to cut 70 out of 276 editorial staff in a bid to make the titles better equipped for what it described as a "dramatically different media economy."
NUJ Scottish Organiser Paul Holleran said more than 40 staff members had since applied for voluntary redundancy.
But he accused Trinity Mirror of refusing to accept a compromise solution which would avoid 30 compulsory redundancies.
Work to rule
Mr Holleran said: "It is beyond logic that the senior management team are refusing to accept our offer of a compromise.
"They appear to be implementing the selection process for compulsory redundancies and have held a series of meetings ahead of their own timetable, acting in undue haste in my opinion.
"They must realise that anyone being identified for compulsory redundancy will trigger an escalation and seriously damage the trust and goodwill of staff for the foreseeable future."
A spokesman for the Daily Record and Sunday Mail Ltd, said: "The editorial restructure is a response to the current economic environment and the rapidly changing media landscape.
"While we have been working hard to achieve the reduction of staff numbers by voluntary means we cannot rule out compulsory redundancies.
"We fully appreciate that this is difficult for all involved, but it is absolutely vital that we take action now to safeguard the future of our newspapers."
Of the 200 NUJ ballot papers returned, 85% backed strike action. Union members are also to implement a work to rule.
The Daily Record's circulation has dropped to about 336,000, allowing it to be overtaken by the Scottish Sun as Scotland's most-bought daily newspaper, according to official ABC figures.
The circulation of the Sunday Mail has also fallen in recent times to a current level of 416,169, but it has retained its position as the country's most popular Sunday newspaper.