PANAMA CITY, JULY 8 -- Opposition protesters, adding new tension to a month-long crisis, took to the streets today in horn-tooting car caravans in defiance of a presidential decree issued late last night prohibiting public protests.

Meanwhile, in an unusual display of dissent within the government, the vice president, Roderick Esquivel, called on President Eric Arturo Delvalle to form an independent commission to investigate public accusations raised against the top military commander, Gen. Manuel Antonio Noriega.

The events revealed sharp rifts within progovernment forces over how to manage the continuing turmoil while the mainly middle-class opposition, which is demanding that Noriega step down, gathered momentum.

Delvalle on Sunday ordered an investigation of the accusations against Noriega, but his move has been criticized by the opposition because he did not appoint an independent prosecutor.

Delvalle's surprise decree prohibiting protests was read by his spokesman over national television last night. It apparently was aimed at a progovernment, anti-American rally scheduled for Thursday that was expected to draw more than 100,000 supporters of Noriega -- the real power in a government in which Delvalle has been largely a figurehead. Organizers promised a high-spirited denunciation of what they alleged is U.S. intervention in Panama's affairs.

The decree also banned an opposition counter-rally planned for Friday. It warned that the authorities would take "the necessary measures" to stop political gatherings that "might interrupt traffic."

Delvalle's statement said he feared violence could erupt during the rallies, which were shaping up as a popularity test for both sides. In a communique, the Democratic Revolutionary Party, which is aligned with the Defense Forces, agreed to suspend the rally and put its members on alert for a new call to action. The party appeared to have been caught off guard.

Sharp debates raged for days inside the main progovernment party after leftist party leaders called last week for the confiscation of some opposition figures' property and for stepped-up anti-American actions.

It remained unclear how or why Delvalle's decision was made. The Defense Forces' television station had no news of it late yesterday, and the two Noriega-controlled dailies did not carry it this morning.

In the hours before Delvalle's decree, progovernment civilian gunmen firing rifle rounds broke up an opposition car caravan on the Via Brazil, a main thoroughfare. Until last month, Panama had seen an extended period of politics marked by little gunfire and few killings.

The trouble began in early June when Noriega's former second-in-command, Col. Roberto Diaz Herrera, was forced out of the military. He accused Noriega of being involved in assassination, graft and electoral fraud. A new round of disturbances followed a U.S. Senate resolution on June 26 calling for Noriega to step down pending an independent investigation into the accusations.

The National Civic Crusade, the opposition coalition of business and professional groups, consulted lawyers today to determine if Delvalle has the power under the constitution to cancel the Friday rally. Crusade spokesmen said the car caravans and waving of white handkerchiefs will continue.

"We feel the demonstrations and caravans will go on anyway," said Crusade leader Rolando de la Guardia. "It will weaken the movement to try to stop those spontaneous actions."

The government has been at a stand-off with the opposition this week. Progovernment forces called for a dialogue but refused to discuss Noriega's resignation. The opposition said Noriega must step down before any dialogue can begin.

Vice President Esquivel, who also heads the Liberal Party that forms part of the governing coalition, called on Delvalle to "govern, start governing the country with the laws and the constitution." He challenged Delvalle to hold Cabinet meetings without the approval or presence of Noriega's representatives and to dismiss any officer who objects.

The U.S. Embassy will be reduced to a skeleton staff Thursday, a spokesperson said. The consulate and the library of the U.S. Information Service remain closed after they were damaged June 30 by rock-throwing progovernment rioters.