BANGKOK - Thailand's government has warned thousands of protesters that more violence could erupt if the entrenched demonstrations that have paralyzed areas of the capital for nearly two months did not end soon.

The warning Saturday followed double nighttime attacks that killed two policemen and wounded 13 people, denting hopes that a reconciliation plan offered by the government last week would resolve the crisis peacefully.

The so-called Red Shirts said they would unveil their own proposal to resolve the crisis in the next few days, pledging it would be flexible and open to negotiations. Nattawut Saikua, a protest leader, said he agreed with the government that the reconciliation process should be finalized by May 15.

But government spokesman Panithan Wattanayagorn earlier said if the protesters didn't end their occupation of Bangkok's prime commercial district "some people who don't wish to see reconciliation take place may take this opportunity to launch another attack."

He described the unknown assailants responsible for several attacks in the capital as "ill-intentioned people who used terror to try to ruin the conciliatory atmosphere." Violence tied to the protest -- including clashes between demonstrators and security forces -- has killed 29 people and wounded nearly 1,000.

The protesters say they agree in principle with a proposal by Prime Minister Abhisit Vejjajiva to dissolve Parliament and hold new polls -- their key demands -- but want more specific details including the exact date for the dissolution.

"One mouth speaks of reconciliation while the other 99 mouths keep talking about cracking down," Weng Tojirakarn, a protest leader, said.

He called on the government to revoke emergency decrees that give the military powers to restore order and that ban public gatherings.

As Weng spoke, a long column of pickup trucks loaded with protesters arrived from northeastern Thailand to reinforce the Red Shirt "occupation zone."

Late Friday night, the relative calm that had prevailed for several days was broken by more violence near where grenades exploded on April 22 and killed one person and wounded dozens. The area, a short distance from the Red Shirt encampment, is guarded by many police and soldiers.

A witness, Decha Phoonpanang, said either a small explosive or gunshots whizzed past him, shattering the glass storefront of a bank and hitting two policemen -- one in the stomach -- and a man in the leg.

Slightly more than two hours later, about three explosions could be heard in an adjacent street that fronts a park, with police officers saying they believed them to be grenades.

The official Erawan Emergency Center on Saturday said two policemen were killed. Most of those wounded were believed to be police.

Other activists who oppose the Red Shirts have denounced the government's peace offering as a capitulation and have demanded that Abhisit clear their encampments or step down.

The standoff in Bangkok has hammered the economy, decimated the tourist industry and ground government machinery to a near halt.