Fears of sectarian violence in Yemen were heightened Friday after suicide attacks on two Shiite mosques in the capital, Sanaa, which killed at least 130 people and left more than 300 wounded. Both of the mosques serve members of the country’s minority Zaidi Shiite sect, which is followed by the Houthi rebel movement that has recently become the most powerful force in the country. At least one prominent Houthi religious leader was reported to have been killed in the attack.

While there were no immediate claims of responsibility, recent months have seen increasing violence by Sunni extremists against Shiite supporters of the Houthis, who forced Yemeni President Abd-Rabbu Mansour Hadi to step down in January after seizing the capital.

Houthi Gains

The Houthis, also known as Ansar Allah (Partisans of God), have long complained of being marginalized in the majority-Sunni country. Nearly one-third of Yemen’s population also belongs to their Zaidi sect of Shi’ism, whose traditions Houthis have attempted to protect in the face of threats by Sunni militants.

The group takes its name from Hussein Badr al-Din al-Houthi, who led the group’s first uprising in 2004 in an attempt to gain greater autonomy for the northern Saada province from which the group hails. Following Houthi’s killing at the hands of the Yemeni military in late 2004, members of his family took control of the group, leading five more rebellions before signing a ceasefire with the government in 2010.

When Yemen’s anti-government demonstrations began during the Arab Spring in 2011, the Houthis joined the protest movement against then-President Ali Abdallah Saleh, capitalizing on the government’s instability to expand their power in Saada and the neighboring Amran province.

From this growing position of strength, the group’s current leader Abdul Malik al-Houthi demanded in August that President Hadi cancel proposed subsidy cuts, in a call that was supported by thousands of Houthi protesters who began sit-ins around government buildings in Sanaa. The protests turned violent after security forces opened fire on protesters, prompting Houthi rebels to seize parts of the capital in September.

Over the following months, the rebels tightened their grip on the capital, culminating in the seizure of the presidential palace in January. Hadi was put under house arrest but later fled to the southern city of Aden, where he declared himself to still be president.

Factional Struggles

Hadi, who was elected in 2012, is largely supported by the international community. As a Sunni, the leader also continues to have support from much of the country’s Sunni majority, though he has been criticized for weakness in the face of Yemen’s deteriorating security and economic challenges.

Hadi’s supporters are not the only ones who have opposed the Houthis. One of the group’s biggest rivals in the country is al Qaeda in the Arabian Peninsula, one of the global jihadist movement’s most dangerous affiliates. While the Houthi movement has primarily focused its energies on challenging Yemen’s central government, it has also increasingly confronted AQAP, even expanding its campaign against the Sunni jihadists in parts of the center and south of Yemen.

The Houthis’ effective takeover of the country in January has only intensified the showdown between the two groups, with many analysts expecting the move to help strengthen the Sunni jihadist group by further justifying its cause in Yemen. AQAP has vowed to attack Houthi loyalists across the country.

Sectarian Conflict

The escalating confrontation between the Shiite Houthis and the Sunni al-Qaeda extremists has raised fears that Yemen’s security crisis could become a sectarian conflict. While sectarian struggles are common throughout the Middle East, Yemen has largely been seen as unaffected by these dynamics. Despite the wars that were fought between Houthis and President Saleh, the conflict did not have the same sectarian dimension because Saleh also hailed from the Houthis' Zaidi sect.

However, the explicitly sectarian rhetoric being employed by various factions since the takeover, along with attacks on religious buildings like Friday’s, increasingly casts the ongoing conflict in those terms.

Regional Dynamics

In the background of Yemen’s crisis are the regional players who have put their backing behind each faction. The Houthi takeover in January was widely seen as an extension of Iranian regional influence because of the Islamic Republic’s alleged backing of Houthi rebel forces.

Saudi Arabia, Iran’s most significant regional rival, is staunchly opposed to the Houthis, which it deems a terrorist organization. The oil-rich kingdom shares a 1,000 mile-long border (1,600 km) with Yemen and has historically played a robust role in the country’s affairs. Saudi officials directly blamed Iran following the Houthis’ ouster of Hadi, who is backed by Saudi Arabia.

The prospect of a Shiite-controlled state just adjacent to its southern border region is "obviously" something the Saudis fear, said Ghanem Nuseibeh, a Middle East analyst and partner at Cornerstone Global associates in London, in an interview in January. Beyond the close proximity of the threat is the larger Saudi concern around Iran’s growing power in the Middle East, particularly with international negotiations over its nuclear program opening the door for the Islamic Republic to exercise its influence more directly across the region.

Economic Uncertainty

The growing instability exacerbates an already precarious economic and security situation in Yemen. The World Bank suspended its operations in the country this week, following the suspension of aid by dozens of countries as a result of the Houthi seizure of power. The move highlights the dire straits faced by the Yemeni economy, with more than half of the population living under the poverty line. The economy is in a deep recession, expected to plummet more than 10 percent this year, hurt among other things by the suspension of foreign aid.