Staff at Welsh universities are beginning an eight-day strike over pay, conditions and pensions.
Cardiff University, Bangor University and the University of Wales will be affected by the strikes which involve members of the University and College Union (UCU) at 60 UK universities.
They object to increases to pension contributions, casual contracts and a squeeze on wages.
Universities said they had taken steps to protect pensions and pay.
Pickets are expected outside university buildings on Monday, and there are plans for “teach-outs” in Cardiff and Bangor where public talks are held off campus.
This is the second time in two years UCU members have taken strike action, after a 14-day walk-out over pensions in February 2018.
The union said universities had continued to support increased staff contributions to the universities’ superannuation scheme pensions system.
The other strike ballot focused on casual contracts in universities, the gender pay gap and a squeeze on wages.
Union officials said the decision to strike had not been taken lightly.
‘Squeeze of declining salaries’
Doris Merkl-Davies, vice-president of Bangor UCU, said: “A lot of members, including those on permanent full-time contracts, are feeling the squeeze of declining salaries and increasing living costs, but are prepared to fight for fair wages by going on strike and taking a one-off financial hit.”
But Universities UK and the Universities and Colleges Employers Association urged staff to reconsider in an open letter.
“In recent months employers have taken significant steps to protect the value of both pensions and pay because we care about our dedicated and talented staff,” the letter said.
“We are very sorry that the industrial action called by UCU is likely to cause unwelcome disruption to students”.
In open letters to students and staff, Cardiff’s vice-chancellor Colin Riordan offered “sincere apologies” for inconvenience, adding: “My priority throughout the strike period is to ensure that any disruption to education and the student experience is minimised.”
He said most teaching would go ahead but in some areas there would be a “significant impact”.
“I am keen to see this situation resolved as soon as possible, and to avoid further strike action this academic session,” he added.
“As a university we cannot solve these issues on our own.”
He told those striking he “fully respects” their decision, adding: “I also appreciate how difficult this situation is for staff, especially given your commitment and loyalty to your students.”
“I want a solution that meets the needs of employees and employers alike and I will continue to advocate for such an outcome.
“We all know from previous periods of industrial action that emotions can and do run high.
“However, I hope that we will be able to treat one another with dignity, courtesy and respect.”