Islamist militants have taken hold of the northern city of Tikrit, Iraq a day after militants seized Mosul, the second-largest city in the country. 

According to CNN, fighting broke out in Tikrit when the military tried to regain the city. 

According to officials in the neighboring town of Samarra, two police stations in Tikrit were set on fire, and a military base was taken over by militants. The militants are believed to be from the Islamic State in Iraq and Syria, an al-Qaeda-like group that is also known as ISIS. 

According to Samarra sources, the governor of Tikrit's capital, Salaheddin, has gone missing. 

Militants who are suspected to be from ISIS raided the Turkish Embassy in Mosul Wednesday, capturing 48 people, including foreign diplomats. The militants also took over parts of Baiji, the location of Iraq's largest oil refinery. 

Explosions also hit three Shiite areas in Baghdad Wednesday, killing 25 people and injuring 56. A car bomb also exploded near a funeral tent Wednesday in Sadr City, killing 15 people and wounding 34.

More than 500,000 people fled the violence in Mosul after it fell to the militants Wednesday. According to the International Organization for Migration, which has been monitoring the militant takeover, the fighting has caused a "high number of casualties among civilians."

Those escaping the violence can only bring what they can carry in plastic bags. The citizens of Mosul are fleeing to the east or going to the Nineveh province in the Kurish area of Iraq. 

Mosul, a mostly Sunni city of 1.6 million, was taken over by hundreds of the radical Islamists Tuesday after a series of violent clashes over the weekend. 

Iraqi government forces who were trained by the U.S. military fled, leaving militants to control the city. 

In addition to taking over police stations, the militants freed more than 1,000 prisoners from jail. 

ISIS issued a statement that they want to continue the siege into the Nineveh province, and said it aims to "open up the province completely and cleanse it of apostates," according to CNN. 

The parliamentary leader of Iraq blamed Iraqi forces, saying they abandoned their weapons, leaving them open for militants to use. 

Iraqi Prime Minister Nuri al-Maliki said Wednesday that all military leaders who fled the area will be court-martialed. 

The Iraq military has begun fighting back, however, as the Iraq Defense Ministry said the air force has killed a group of ISIS militants in south Samarra. 

"This is not the end, we are very confident that we will be able to correct the path and to overcome mistakes," the ministry said in a statement on its website.

Forces in the Kurdish region also went on the offensive when militants took over villages north and west of the city. 

The regional prime minister of the Kurdish region blamed Iraqi leadership for the collapse of the city. 

"Over the last two days, we tried extremely hard to establish cooperation with the Iraqi Security Forces in order to protect the city of Mosul. Tragically, Baghdad adopted a position which has prevented the establishment of this cooperation," Nechirvan Barzani said in a statement.

Turkish officials told CNN Wednesday that the Turkish Embassy workers held hostage in Mosul are all alive. 

"The condition of the Turkish citizens is fine, developments are being monitored," the officials said. "It is a quite fragile situation, but hopefully we will resolve it today or in a couple days."

Turkey's Foreign Ministry also said that militants abducted 28 Turkish truck drivers taking fuel from Mosul to Turkey on Tuesday.

Officials also said the takeover of Baiji presents a major logistical problem, as Baiji sits on a main highway north from Baghad to Mosul, which passes through rural areas over which ISIS has influence. The government can only reinforce troops in Mosul by driving them through Baiji, and ISIS' control over the area will make it much more difficult for the government to make headway in troop reinforcements. 

Prime Minister al-Maliki condemned the violence Wednesday, calling the takeover of Mosul a "conspiracy" to destabilize the country, and called on Iraqis to stand united. 

He requested parliament declare a state of emergency Tuesday, and urged volunteers to help the army fight the terrorists. 

The fighting is the latest show of resistance stemming from growing discontent in the country. Iraq's minority Sunni population feels shut out of al-Maliki's government, which is dominated by Shias. 

The ISIS takeover is the latest manifestation of the sectarian divisions, which are worsened by Syria's civil war. 

A U.S. counter-terrorism official told CNN that ISIS is trying to expand its influence in both Syria and Iraq. 

"Strategically, the group looks at Syria and Iraq as one interchangeable battlefield, and its ability to shift resources and personnel across the border has measurably strengthened its position in both theaters," the official said. 

However, according to the official, despite the territorial advances it has made, ISIS still has "significant weaknesses."

"It has shown little ability to govern effectively, is generally unpopular and has no sway outside the Sunni community in either Iraq or Syria," the official said. 

However, the increasing discontent felt by Sunnis will make peace difficult to achieve.