KHARTOUM – Sudan's President Omar al-Bashir on Thursday promised his country would respond robustly to what he believes was an Israeli bombing of a Khartoum arms factory and said he was in "perfect health" after undergoing surgery in Saudi Arabia.

Sudan last month accused Israel of carrying out an air strike on the Yarmouk arms factory in the south of Khartoum, causing a blast that killed four people.

Israel has not commented on the charge, but has long accused Sudan of channeling weapons from Iran to the Hamas-controlled Gaza Strip.

"I am in perfect health, and our response to Israel will be painful," state radio quoted Bashir, 68, as saying in a brief text message sent to mobile phones.

Bashir, who came to power in a bloodless 1989 coup, left hospital in Saudi Arabia on Wednesday after undergoing a "small, successful" operation, state media said.

Sudanese blogs and newspapers had begun to speculate about the president's health because he has held fewer public rallies in the past few months. He underwent surgery on his vocal cords in Qatar in August, an official said last month.

Over more than two decades in power, Bashir has weathered multiple armed rebellions, years of US trade sanctions, an arrest warrant from the International Criminal Court, waves of student protests, and the secession of oil-producing South Sudan last year.

He is known for his fiery speeches and for dancing and waving his walking stick at public events.