Thursday's first explosion targeted a Houthi checkpoint and killed at least 47 people. The second occurred outside an army checkpoint and killed 19 soldiers. Both came after Houthi rebels stormed the Yemeni capital, Sanaa, on September 21.

The Shiite rebel group from northern Yemen has been fighting on and off with government forces over the past 10 years, but no one could have predicted that they would so suddenly take control of the capital.

The Houthi's power base is in the mountainous northern Saada province. The group is affiliated with the minority Zaidi sect of Shia Islam, in contrast to the majority of Yemenis, who belong are Sunni. According to the Zaidi's traditional teachings, only direct descendants of the Prophet Muhammad may take over the political and religious leadership of their community. Among these descendants is the Houthi clan, which has led an eponymous protest movement since the 1990s.

Political battle

Ever since the resignation of former President Ali Abdullah Saleh, who led an authoritarian regime for more than 30 years, Yemen has had a national unity government. Supporters of the former president are represented, as are members of the opposition. The opposition is made up of very different groups including revolutionaries, Islamists, and socialists. After Saleh left power, the country's fate has been in the hands of President Abed Rabbo Mansour Hadi. He belongs to the same party as his controversial predecessor, but continues to distance himself from Saleh. Now, he has to deal with Yemen's internal power struggle and the violence - like Thursday's explosions - that often accompanies it.

For 18 years, Hadi was Saleh's deputy. After an attack on Saleh in June 2011, he was named acting president of Yemen. At the start of 2012, almost all the factions in Yemen were united behind Hadi as a compromise candidate, and he was elected as the country's leader. In the following months, a group of politicians took over key political positions and stood up against Saleh, who still wielded considerable power, in the wake of the Arab Spring.

Advance of the Houthis

Among them was one of Saleh's former allies, General Ali Mohsen al-Ahmar, who had the support of part of the army. As a general under Saleh's command, al-Ahmar and the Yemeni armed forces fought against the Houthi - something the rebels from the North have not forgotten. Over the past two years, they have sought to sideline al-Ahmar and his allies. At the same time, the general has been vying with Hadi and Saleh for control of the country.

Al-Ahmar has the support of the revolutionaries and moderate Islamists. The Houthi, on the other hand, are fighting against the general and his allies. Since the start of the year, the Houthi had been encroaching on the capital, Sanaa. When Hadi announced a drastic rise in energy prices in a bid to fill the state's empty coffers, the Houthi seized the opportunity and put themselves at the forefront of a protest movement comprised of almost all of Yemen's political groups.

Storming Sanaa

The Houthi militia has given the protest movement serious clout. They moved into the capital as part of the protesters, and after a short battle with the army units behind al-Ahmar, the Houthi managed to bring Sanaa under their control. There has been no sign of al-Ahmar for a week now. Observers are guessing that he fled to Saudi Arabia, fearing for his life should he remain in Yemen. The Houthi appear to be bent on revenge. In a decade of fighting with government forces, thousands of people lost their lives; the majority of them were Houthi.

Hadi also has an interest in weakening al-Ahmar. That's the only way he can gain influence and expand his political scope. The army factions loyal to Hadi did very little to prevent the Houthi from taking the city - perhaps because the rebels come in handy for the president this time.

Secret alliance?

The thought of weakening al-Ahmar could also well appeal to former President Saleh - after all, al-Ahmar was partly responsible for Saleh's downfall. There is mounting evidence that the former president supported the rebels from the North. Saleh and the Houthi view al-Ahmar, the revolutionaries, and the Islamists as common enemies.

During the Houthi-led demonstrations, the flags of Saleh's party could occasionally be spotted. And after the rebels took Sanaa, the former president changed his profile picture on Facebook. His friends on the social networking site are now greeted by a grinning Ali Abdullah Saleh. But the winner is without doubt rebel leader Abdul-Malik al-Houthi, now an unavoidable force in Yemen. For many Yemenis, the revolution is only just beginning.