Houthi fighters have seized parts of Yemen's southern city of al-Hudaydah, the second most important port after Aden, and the city of Dhamar, while southern secessionists have garnered more support, pushing the country towards the verge of disintegration.
The rebels captured the city's airport and military base, including stockpiles of weapons and ammunition on Tuesday.
The city of al-Hudaydah is vital to Yemen's economy with its strategic location on the Red Sea, where most of Yemen's oil is shipped to international markets. The city is also home to the country's largest oil refinery.
Houthis - Rebel group at war with the government since 2004. Signed a deal with the government last month for more political inclusion after mass protests and bloody clashes.
Al-Islah - Islamist party that draws support and membership from heavily armed Sunni tribesmen, and is instrumental in rallying support behind the army and the government. The Houthis have identified the party as its arch-enemy.
The Southern Separatist Movement - Umbrella group that wants the south to break away from the north and reinstate the former Socialist state that existed until 1990.
Al Jazeera's Hashem Ahelbarra said that if the Houthis controlled the city totally "it would give them more leverage to negotiate any deal in the future".
The Houthis seek to consolidate their grip over the northern part of the country, favouring it to be one region instead of three, while also seeking a bigger say in drafting the constitution.
"Basically, this is a group that is positioning itself as a parallel government to the government - they are everywhere," said Ahelbarra.
But Mohamed Qubaty, the former adviser to the last three Yemeni prime ministers, said that since 95 percent of the city of al-Hudaydah comprises of Sunnis, the Zaidi Houthis may not be able to claim full control over city.
Qubaty said that the Houthis’ strategy "is to precipitate confrontation or crisis and negotiate over it … as it appears, they’re aiming for further concessions".
Houthi rebels also captured Dhamar, a city 100km south of the capital Sanaa, local sources told Al Jazeera.
Reports suggested fighters stormed several government buildings and the city's security headquarters. The rebels reportedly set up checkpoints in Dhamar, similar to the checkpoints they set up in Sanaa.
The Houthis already control the provinces of Saada and Amran north of the capital.
Meanwhile, tens of thousands of secessionists rallied in Aden, in the south. Our correspondent said that if they called for secession, it would be backed by all political factions.
RELATED: Southern movement stages mass rally in Yemen
"For the first time in the country's modern history the Sunni Islah party - which has consistently been pro-union - is saying that they support the right of the south for self-determination," said Ahelbarra.
"The rally raises fears of disintegration if the south decides or chooses to break away in the coming hours," he added.
Source: Al Jazeera