(CNN) -- Gunmen who stormed an Iraqi university on Saturday used students as human shields and clashed with security forces, authorities said.
Forces have surrounded al-Anbar University in the city of Ramadi and are attempting to retake the campus from the attackers.
The campus is about 110 kilometers (68 miles) west of Baghdad.
The gunmen are believed to be members of the Islamic State in Iraq and Syria, a rogue Sunni Muslim extremist group formerly affiliated with al Qaeda, also known by its acronym ISIS, police said.
Approximately 1,200 students, professors and staff who live in the campus residential buildings were present during the attack; nearly 20 students were slightly injured, officials said.
The majority of students were able to flee, but some are still inside, police officials told CNN.
The Al-Anbar University attack comes amid a wave of violence that has taken Iraq by storm.
Also Saturday, six roadside bombs exploded in the capital of Baghdad, killing at least 33 people and injuring 72 others, police officials said.
The explosions occurred in a busy commercial Shiite neighborhood, targeting mostly civilians, police said.
This year, Iraq has witnessed some of the worst violence since 2008. The United Nations reported that May was the deadliest month since the beginning of the year.
The escalating violence in recent months has left hundreds dead, raising fears it could return Iraq to the level of violence in 2006 and 2007, when bodies littered the streets.