Yemen's acting leader says President Ali Abdullah Saleh was so severely wounded in an attack on his presidential compound earlier this month that it is uncertain when he will return from Saudi Arabia, where he is undergoing medical treatment.

Vice President Abed Rabbo Mansour Hadi told CNN Wednesday that he saw Mr. Saleh immediately after the bomb attack and that the Yemeni leader had a piece of wood in his chest and burns to his face, arms and upper body.

He said it “could be months” before Mr. Saleh returns and that the decision is up to his doctors.

Earlier Wednesday, the Yemeni leader instructed his deputy to hold talks with political opponents on a regional plan for a transition of power. The country's main opposition coalition, however, dismissed the announcement.

Foreign Minister Abu Bakr al-Qirbi said Wednesday on Yemeni state television that he had visited Mr. Saleh in the hospital and the two had discussed the Gulf Cooperation Council initiative and the country's political crisis.

The U.S.-backed plan calls for Mr. Saleh to give up power in exchange for immunity from prosecution. The Yemeni president has agreed to the deal three times in recent months, refusing at the last minute each time to sign an accord.

Opposition spokesman Mohammed Qahtan said the country's dire economic and security situation does not allow for more meetings and negotiations. He said Mr. Saleh should immediately transfer power before any dialogue can take place.

Yemeni officials had said Mr. Saleh would make his first public appearance since the palace attack this week, but Wednesday they said that plan was delayed on the advice of his doctors.

Tens of thousands of Yemenis demonstrated Wednesday in the capital, Sana'a, and six other major cities demanding Mr. Saleh's ouster.

Protest organizers reported that about 320 members of Yemen's security forces defected to the opposition, including 150 from the elite Republican Guards. Government officials have not confirmed the mutiny.

A series of defections by security forces have taken place since anti-government protests began in February.

Also Wednesday, military officials said at least 26 soldiers and 14 Islamist militants were killed in heavy fighting in the southern city of Zinjibar as the two sides battled for control of a stadium on the outskirts of the city.