University students are facing fresh disruption as academics and administrative staff stage a third day of strike action in a bitter dispute over pay.
Members of four unions - Unite, Unison, the University and College Union (UCU) and EIS in Scotland - are taking part in a national walkout.
Institutions across the UK could face disruption with the possibility of lectures, seminars, workshops and tutorials cancelled or postponed as academics with support staff such as technicians administrators, caterers and cleaners join picket lines.
University employers have previously said that they are disappointed that another strike has been called, adding that institutions are reporting ''low to no support'' for the walkout.
The dispute centres on a 1% pay rise offered to university staff - including lecturers, technicians and administration workers - which the unions insist means there has been a 13% pay cut in real terms since October 2008.
Unison general secretary, Dave Prentis, said: "For low paid workers it is a very difficult choice to take strike action, so the decision to walk out for a third time shows the depth of feeling amongst our members. Hard working staff have dealt with significant changes that increased their workloads dramatically, yet their incomes have been squeezed to breaking point."
The latest walkout is a further escalation of the unions' industrial action over the 1% pay offer.
Two one-day national strikes were staged in the autumn, and the UCU is holding a series of two-hour stoppages which it says is aimed at disrupting teaching.
UCU general secretary, Sally Hunt, said: "Staff are angry they've had to endure real-terms pay cuts while those at the top continue to enjoy healthy rises. Research shows that our universities are performing at the very top on the global stage, yet our staff are being paid far less than those in competitor countries.
"It's time for fair pay for all in our universities. Taking strike action is always a last resort and we would urge any students frustrated or annoyed at the disruption to contact their vice-chancellor and ask them to put pressure on them to come back to the negotiating table with a fair pay offer."
A spokesman for the Universities and Colleges Employers Association (UCEA) said: "Higher education (HE) institutions will be disappointed to see the four trade unions' latest attempt in the face of dwindling support to call for yet another strike day aimed at damaging students' education.
"It is equally disappointing to see the trade unions wilfully painting a misleading picture of HE institutions' financial conditions as part of their tactics for pay negotiations. The average 3% increase in pay at HE institutions last year was at the limits of affordability.
"The trade unions also know that the pay and conditions for the lower paid are often amongst the best in our HE institutions' localities.
"All HE institutions are consistently clear that there is no scope for further pay increases beyond those paid last year, and all are united in their commitment to protect students' education."