Kigali - There will be no spur of the moment Twitter rants by Rwanda's presidential candidates, as the election commission has ruled that it must pre-approve all of their social media updates."We are asking (candidates) to present us their messages, their drafts" to verify that they are not against the law," electoral commission head Kalisa Mbanda told AFP on Monday.The measure, published in the government gazette earlier this month, will be effective as from the start of the official campaign on July 14 and concerns "messages, photographs and other campaign material" published on social networks.Any social media messages will have to be submitted to the seven election commissioners at least 48 hours before their publication."If the message is not accepted it cannot be published," said Mbanda.He said the goal was to "prevent declarations, words, acts that can lead the population to acts of insecurity that could divide the Rwandan population."The measure has been criticised by the opposition, who fears it is a tool to prevent criticism of President Paul Kagame who is seeking re-election in August after the constitution was changed to allow him to run again."It is unfair because we think social media should be something spontaneous so if someone wants to control it or to approve it first it is going to make our work very difficult," said Frank Habineza, leader of the tiny opposition Democratic Green Party."If there is some message that is very critical to the ruling party maybe they can stop it saying it is against national security or something like that," he added.Habineza, who is one of only four candidates who have declared their intention to run against Kagame - pending the election commission's approval - said he was considering legal action.Since the end of the 1994 genocide in which around 800 000 mostly Tutsi people died, Rwanda has been praised for its stability and economic performance. However it often comes under fire for a lack of political freedom.Rwanda is constitutionally a multi-party system but there is practically no opposition within the country.All recognised parties generally support the policy decisions made by the ruling Rwandan Patriotic Front (RPF) - with the exception of Habineza's Democratic Green Party which was the only one to object to the 2015 constitution changes allowing Kagame to seek re-election.Kagame has been in charge since taking power at the head of a rebel army in 1994 and has already served two seven-year terms as president.Kagame won previous elections with well over 90% of the vote.