Seven people were injured, two of them critically, after a shooting attack on a bus in Jerusalem's Old City, Israeli police and medics said early Sunday.

"The police were informed of a shooting of a bus ... Police have cordoned off the scene and are searching for a suspect who fled," the police said.

Israel's emergency medical services, the Magen David Adom (MDA), called the incident a "terror attack in the Old City".

"We were on scene very quickly. On Ma'ale Hashalom St. we saw a passenger bus standing in the middle of the road, bystanders called us to treat two males around 30 years old who were on the bus with gunshot wounds," MDA paramedics said in a statement.

Bus driver Daniel Kanievsky said the attack occurred near King David's Tomb.

"I was coming from the Western Wall. The bus was full of passengers. I stopped at the station of the Tomb of David. At this moment starts the shootings. Two people outside I see falling, two inside were bleeding. Everybody panicked," he told reporters at the scene.

Since March, 19 people -- mostly Israeli civilians inside Israel -- have been killed in attacks mostly by Palestinians. Three Israeli Arab attackers were also killed.

In the aftermath, Israeli authorities increased operations in the occupied West Bank.

More than 50 Palestinians have been killed, including fighters and civilians, in operations and incidents in the West Bank since then.

Last week saw three days of intense conflict between Israel and Islamic Jihad militants in the densely populated Palestinian enclave of Gaza.

At least 49 Palestinians, including Islamic Jihad fighters but also children, died in the latest violence, which ended last Sunday after Egypt negotiated a truce.