The campaign for the first round of France`s presidential election has officially started, with advertising allowed for each of the 10 candidates, according to BBC.

The first radio and TV advertisements were broadcast on Monday and posters have begun appearing on local authority noticeboards across the country.

President Nicolas Sarkozy is ahead in the opinion polls for the first round but Socialist rival Francois Hollande is predicted to win the second round.

Campaigning is due to end on 21 April.

The first round takes place the following day, with the run-off on 6 May.

The 10 candidates are allowed a strict 43 minutes of campaigning on television before 20 April and they are banned from seeking donation and from denigrating their opponents, under the strict rules of the audio-visual authority (CSA).

Each candidate is given 18 slots, 10 lasting 90 seconds and eight lasting three-and-a-half minutes. According to the CSA, more than 13 million French viewers watched the shorter clips before the first round of the 2007 presidential election.

Centrist candidate Francois Bayrou had the first campaign advertisement on air early on Monday, despite being 10,000km (6,000 miles) from Paris, on the Indian Ocean island of Reunion, at the time.