NAIROBI, Kenya (CNN) -- Aid agency Medecins Sans Frontieres (MSF) accused the Sudanese government of bombing a civilian hospital in southern Sudan on Wednesday as part of a campaign to target the civilian population.

MSF said five bombs were dropped on or by its hospital compound in Kajo Keji in Western Equatoria Province on Wednesday afternoon, destroying the immunization block and causing extensive damage to surgical and outpatient departments.

There were no casualties.

The raid follows the systematic bombing of four other civilian hospitals in the Equatoria region in the last month and a half, MSF said in a statement late on Wednesday.

"This is a deplorable act which clearly targets civilians and medical assistance to the civilian population," said Ettore Larici, the head of MSF's mission in south Sudan.

"MSF questions whether this is a deliberate policy of the government of Sudan to target civilian populations and hospitals."

MSF said the hospital served 90,000 people, with half of its 60 beds reserved for children.

Roughly 1.5 million people are thought to have died as a result of Sudan's 15-year civil war, which broadly pits the largely Arab, Muslim north against the mainly Christian or animist South.

Aid agencies pumped hundreds of millions of dollars into the south last year to combat drought and war-related famine.

This week, the battle against the famine faces a major test as U.N. officials try to pursuade warring parties to extend a six-month cease-fire they say is crucial to keeping thousands of people alive.

Tom Vraalsen, a special envoy of the U.N. secretary-general, lobbied government officials in Sudan's capital, Khartoum, earlier this week and flew to Nairobi on Wednesday to meet leaders of the rebel Sudan People's Liberation Army (SPLA) in a bid to win a new cease-fire deal for the vast southwestern region of Bahr el Ghazal.

The current cease-fire expires on Friday and both sides have so far declined to commit to an extension.

"An escalation of fighting will strike a deadly blow to thousands of extremely fragile people," Catherine Bertini, executive director of the U.N. World Food Program, said in a statement.

Hundreds of thousands of people were forced to flee their homes when fighting broke out in Bahr el Ghazal early last year and the widespread disruption of agriculture sparked a famine which killed thousands.

Reuters contributed to this report.