BEIJING - China's state broadcaster issued an apology on Sunday after parents complained that a compulsory television programme targeted at millions of school children was preceded by almost a quarter of an hour of non-stop advertising.

All elementary and middle school students and their parents were told by the education ministry to watch the programme "First Lesson of New Semester" at 8 p.m. (1200 GMT) on Saturday.

The programme, produced by CCTV and the education ministry since 2008, is aired on Sept. 1 every year to mark the start of the new school calendar after a two-month summer break. This year, the programme focused on the "spirit of creativity" as China observed its 40th year of opening up.

But TV viewers had to sit through 12 minutes of advertisements on cars and scooters, home appliances, toothpaste and stationery.

"We sincerely apologise to parents and students for the long TV commercials ahead of the programme," the state broadcaster CCTV wrote on Weibo, a popular Twitter-like microblog.

The commercials were dominated by ads on after-school tutoring in a country where a growing middle class is able to afford extra classes aimed at improving the chances of getting better grades and a stab at scholastic glory.

"Are you so short of money?" wrote one Weibo user.

The outcry over the commercials coincided with protests by parents over the weekend in a city in southern China about school enrolment.

Police on Sunday detained 46 people in Leiyang city in Hunan province after bottles, bricks and firecrackers were thrown at officers and government officials during a 600-strong protest.

Many parents also expressed disapproval over the choice of an all-male pop band for the programme's opening musical act, saying they were too "effeminate".

"Can we find someone who is more masculine? If our youth is effeminate, so will the country be," one angry parent wrote on Weibo.