MONROVIA (AFP) - Gunmen have killed Keith Jubah, a close aide to Liberia's President Ellen Johnson Sirleaf, in an overnight attack, his family and officials said Monday.

According to the president's office, two suspects in the west African country have already been arrested.

Jubah, the head of Liberia's Public Procurement and Concession Commission (PPCC), was shot as he returned to his home in Kakata, about 20 kilometres (12 miles) from Monrovia, said one of his sisters, Hawa Kwiyateh.

"They shot him, cut his body all over with cutlass and tried to set the body ablaze," Kwiyateh said in tears.

In confirming Jubah's death, the president's office gave no clue as to the possible motive for the attack. Armed robbery appeared to be ruled out, since nothing was stolen.

"His watch, his wallet, money, every belonging was left intact in the car," Kwiyateh said.

The PPCC is the government office responsible for the privatization of all state properties, the monitoring of all concessions signed by the government, and the procurement of all state projects.

Jubah was a confidant of the president and an influential member of the ruling Unity Party.

"The president is very shocked," Sirleaf's Press Secretary Cyrus Badio told AFP. "She cannot understand why one of the people she considers as good public servants in her government would die in such a way."

"She said no stone will be left unturned to find the perpetrators. As matter of fact, two of them have already been arrested," Badio added, without giving further details of those arrested or how many people investigators thought may be involved.

Police also said simply that two people had been arrested.