College lecturers have gone on strike in a long-running dispute over pay and conditions.

The Educational Institute of Scotland (EIS) said members would walk out over the refusal of management to honour a deal that was reached more than a year ago.

The agreement promised equal pay for lecturers in all colleges and national terms and conditions following years of pay inequity for lecturers doing the same jobs in different colleges, the EIS said.

The strike comes after a 96% vote in favour of the action in a recent ballot of Further Education Lecturers' Association (EIS-FELA) members.

More than 4600 members are eligible to take part in the strike, which will affect about 20 institutions.

EIS general secretary Larry Flanagan said: "After more than a year of waiting and watching college managers talk down the agreement that they freely signed up to, Scotland's further education lecturers have simply had enough.

"All that lecturers are asking is for the deal that was agreed by both sides to be honoured.

"Sadly, rather than working to deliver their commitments, college management have spent the last 13 months attempting to rewrite history and airbrush this binding agreement while simultaneously denigrating the hard-working lecturing staff in their colleges."

Picket lines will be in place at all colleges across Scotland covered by the 2016 National Joint Negotiating Committee (NJNC) agreement.

The EIS said Thursday's walk-out is the first day in a continuing and escalating programme of strike action.

A further one-day action is planned for next Wednesday, with the strike then escalating to two days per week and then three days per week unless the deal is honoured.

A demonstration will also take place outside the Scottish Parliament at 1pm on Thursday.

A spokesman for the Colleges Scotland Employers' Association said: "It is hugely disappointing that the EIS is taking strike action that will affect college students at this critical time.

"Colleges across Scotland are doing everything they can to minimise the disruption to students, who are currently preparing for their exams and finishing coursework.

"The strike is completely unnecessary and inappropriate at a time when we are currently engaged in Acas talks with the EIS to try and resolve this dispute."