The Uganda parliament has passed a law that imposes a controversial tax on people using social media platforms.

It involves a daily charge of 200 shillings [$ 0.05, £ 0.04] on people using Internet messaging platforms such as Facebook, WhatsApp, Viber and Twitter.

President Yoweri Museveni had pushed for change, arguing that social media encouraged gossip.

The law should come into force on July 1, but doubts remain about how it will be implemented.

The new excise law (amendment) will also impose various other taxes, including a 1% levy on the total value of mobile money transactions - which civil society groups complain will affect Ugandan poor who rarely use banking services.

State Finance Minister David Bahati told parliament that tax increases were needed to help Uganda settle its growing national debt.

Experts and at least one major internet service provider have raised doubts about how a daily social media tax will be levied, reports Catherine Byaruhanga from the BBC from Uganda.

The government is struggling to ensure that all mobile phone SIM cards are properly registered.

And of the 23.6 million mobile subscribers in the country, only 17 million use the Internet, Reuters reports.

It is therefore not clear how authorities will be able to identify Ugandans who access social media sites.

Museveni pushed for the social media law in March. He wrote a letter to Finance Minister Matia Kasaija insisting that the revenue from the social media tax would help the country "cope with the consequences of the olugambo [gossip]".

But he argued that there should be no tax on Internet data as it was useful for "educational, research or referral purposes".

Critics at the time said that the law would reduce freedom of expression.

Kasaija rejected concerns that the new law could restrict people's use of the Internet.

"We are looking for money to maintain the security of the country and extend electricity so that people can enjoy more social media, more often, more frequently," he told Reuters in March.

Social media has become an important political tool in Uganda for both the ruling party and the opposition, our correspondent says.

Access to the platforms was closed during the 2016 presidential elections. President Museveni insisted when it was done to "stop spreading lies".

Other East African countries are approving laws criticized by activists who influence freedom of expression.

On November 29, the Tanzanian government won judicial proceedings against opponents of new regulations that require bloggers to pay a fee and disclose their financiers.

In Kenya, a new law on cybercrime entered into force on May 30th.

Journalists and bloggers have managed to get the court order to suspend some parts of the law including clauses on the dissemination of "false" information, which they claim is an attempt to muzzle on independent media.