Social media users across Yemen are reporting limited or no access to Twitter, Facebook, and YouTube, raising fears the sites could be blocked.

A Twitter post by blogger Haykal Bafana said several websites had been down since midday on Saturday, with more reports filtering through out the afternoon.

Cities where Twitter was reported to be inaccessible included the capital, Sanaa, Hodeidah on the country's Red Sea coast, and Taiz in the south.

While some users reported being able to access Facebook and YouTube, Twitter could not be reached without using Virtual Private Network (VPN) software, which routes a user's connection through servers in another country.

Okay, so far Twitter basically seems to be blocked nationwide. However Facebook & YouTube are blocked in some areas only. #Yemen Peachy! — Hisham Al-Omeisy (@omeisy) May 30, 2015

It is not known whether the websites were being blocked, but user Khaled Ahmed Alradhi said he had contacted people working for Yemeni communications provider, TeleYemen, who said the company was not blocking content.

"I called everybody I know in TeleYemen, and they all confirmed it's not them," Alradhi wrote in a post on Twitter, which he said he accessed through a VPN.

Many users expressed fears that the sites were being blocked by either the Saudi government, or Houthi rebels, while others suggested technical failure could be behind the outages.

"Let's not jump (the) gun here by accusing shady secret orgs for Twitter block," said one user, Hisham al-Omeisy.

Yemen is experiencing a conflict between Houthi rebels, who control the capital Sanaa and large swathes of the state, and supporters of President Abd-Rabbu Mansour Hadi, who are backed by airpower from a coalition of Arab states.

#Breaking Twitter in #Yemen closed down to all users since noon. I am lucky my internet connection is directly through satellites. #اليمن — Arwa Al-Anesi (@ArwaAlAnesi) May 30, 2015