A prominent Yemeni activist who used social media to document the war that has ravaged his country has been released by Houthi rebels after more than five months in detention.

Hisham al-Omeisy, 38, was freed on Monday along with two other prisoners accused of being loyal to Yemen's slain former President Ali Abdullah Saleh, sources told the Yemen monitor website.

The political analyst and father of two was reportedly captured without charge on August 14, in the capital Sanaa, by more than a dozen armed security officers from the National Security Bureau.

A number of international rights groups, including Amnesty International and Human Rights Watch, had condemned the arrest and demanded al-Omeisy's release.

Al-Omeisy, who has 35,600 followers on Twitter, has appeared several times as a commentator on Al Jazeera and used social media to document the war in Yemen.

Following his release, pictures of al-Omeisy hugging and greeting his two sons emerged on Twitter.

Those moments when a dear friend is released from prison are the best moments ever, ones you never forget, makes all the struggle worthwhile. Today we celebrate a #FreeHisham @omeisy pic.twitter.com/3iSZWxWNsY — Jamila Hanan (@JamilaHanan) January 15, 2018

Middle East journalists, rights activists and social media users welcomed the news on Twitter.

Al-Omeisy has been a vocal critic of all parties involved his country's civil war, now its fourth year.

His last post on Twitter before detention criticised the military and "corrupt" officials.

"Armed goons backed by corrupt officials are forcefully taking real estate properties in Sana'a," the tweet on August 12 read. "They just showed up at my door."

Yemen has been torn apart by a civil war, which began in September 2014, when rebel Houthi fighters stormed into the capital and overthrew President Abd-Rabbu Mansour Hadi's internationally recognised government.

In March 2015, the Saudi-led coalition began a campaign against Houthi forces allied with overthrown President Ali Abdullah Saleh in support of Hadi's government.

Since then, the Houthis, who are believed to backed by Iran, have been dislodged from most of the south, but remain in control of Sanaa and much of the north.

With war still raging, at least 10,000 people killed and widespread famine, Yemen has been described as the worst humanitarian crisis in the world by the UN.