RAMALLAH, West Bank - Palestinian leader Yasser Arafat today ordered an investigation into the shooting of a key critic of his unrelenting grip on power as Palestinian officials warned of dire consequences for law and order in their territory.

Nabil Amr, a lawmaker seriously wounded by a sniper's bullets, issued a plea for calm and hinted that someone was trying to silence him.

A sniper shot Amr in the West Bank city of Ramallah late Tuesday. An advocate of reforms for years, Amr had increased his criticism of Arafat in recent days as the leader refused to relax his control over security forces.

Palestinian officials condemned the shooting and warned of serious ramifications. A spate of kidnappings and riots plunged the West Bank and Gaza Strip into turmoil in recent days, leading to a reshuffling of the Palestinian security forces and the resignation of the prime minister.

"If we can't restore public order and law ... this will bring the greatest damage to the Palestinian people and their cause," said senior Palestinian Cabinet Minister Saeb Erekat. "It's the whole social fabric that is collapsing now."

Arafat ordered police to open an investigation into the shooting, said the governor of Ramallah, Mustafa Eisa. The assailant's identity was not known. Some Palestinian analysts said Arafat's supporters were interested in silencing critics of his authority.

The shooting came hours after Prime Minister Ahmed Qureia refused to retract his resignation if Arafat does not share power with his Cabinet, further throwing the government into crisis. Arafat has rejected the resignation, leaving Qureia's status in limbo.

"This is proof that this curse must be stopped," Qureia said today about the recent violence, while on his way to visit Amr. "This is a blow to us all, not just to Nabil. This must be investigated and we will investigate."

Israel, the United States and backers of Mideast peace have pressed Arafat to relinquish some of his absolute authority. Israel blames Arafat for nearly four years of fighting, accusing him of refusing to rein in militant organizations.

In the shooting late Tuesday, a sniper fired four bullets from close range toward Amr from the open window of a balcony at his home in a wealthy Ramallah neighborhood, said his son, Tarek. Two bullets hit Amr in the leg.

Doctors said Amr's right leg might need to be amputated below the knee since no muscle or nerves remained in the area.

Amr has pressed actively for reforms, and his house had been shot at two years ago when he was working to unite Arafat critics. An adviser to former Prime Minister Mahmoud Abbas, Amr has also pushed for an end to the fighting with Israel.