People and security officials walk and look as smoke rises from a tourist bus in the Red Sea resort town of Taba in the south Sinai, February 16, 2014. [Photo/Agencies]

CAIRO -- At least four people, including three South Korean nationals were killed, and 13 others injured in a bus explosion on Sunday on the Egypt's Taba border crossing in Sinai Peninsula, the Egyptian Health Ministry spokesman Ahmed Kamel told Xinhua.

The interior ministry said in a statement that "the tourist bus was waiting at Taba border crossing when its front part exploded."

The tourist bus was carrying 33 tourists from the Republic of Korea (ROK) who visited Saint Katherine Monastery, official news agency MENA quoted a police source as saying.

The Egyptian bus driver was also killed in the blast and the casualties are likely to increase, Khalid Abou Hesham, head of the South Sinai's Ambulance Authority, told Xinhua, adding "the cause of the blast is still unclear."

Since Egypt's former Islamist-oriented president Mohamed Morsi was ousted by the military last July, some radical militants took the peninsula neighboring Israel as a stronghold for launching attacks.

Over the past few months, the Egyptian army launched large- scale security operations in coordination with police to uproot terrorist hideouts in the peninsula.