Demonstrations and violence continued across Syria on Friday, as opponents of the government condemned the Arab League and world powers for failing to help them, while opposition groups outside the country prepared to meet with diplomats for a “Friends of Syria” conference in Istanbul.

Members of revolutionary organizations inside Syria expressed anger at the slow pace of diplomatic attempts to halt violence that the United Nations estimates has killed 9,000 people , after nearly a week of calls by international leaders for Syrian President Bashar al-Assad to implement a U.N.-forged plan for peace.

“We are under shelling every day, and we need food, medication and all the help in the world,” said an activist in the opposition-dominated city of Homs, who gave his name as Waleed Fares. “All the initiatives are coming late.”

The U.N. proposal, which calls for Syrian forces to halt hostilities in population centers , was endorsed this week by Assad. “The deadline is now,” said the spokesman for U.N. envoy Kofi Annan, Ahmad Fawzi, while speaking in Geneva. “We expect him to implement this plan immediately.”

But Fares said that there had been no letup in heavy artillery fire on his neighborhood of Khalidiyeh, and dozens of deaths were reported across the country by activist groups. Syrian news media reported that four explosive devices had been found and defused in the northern city of Aleppo on Thursday.

Opposition groups, which are largely based outside Syria and have struggled for unity, prepared to gather in Istanbul on Sunday to lobby nations sympathetic to their goals. U.S. Secretary of State Hillary Rodham Clinton, who was in Saudi Arabia on Friday meeting with King Abdullah, is expected to be among those attending.

But rebels inside Syria criticized their representatives for being out of touch.

“The Syrian opposition is a big shame,” said Noureddine al-Abdo, a member of the opposition in Idlib province who said he was moving from village to village with the armed opposition known as the Free Syrian Army. “They didn’t do anything for the Syrian people — neither them nor anyone in the world.”

Other activists inside the country said they welcomed American and British moves this week to supply the opposition on the ground with non-lethal aid, but some said that what they really want is weapons.

“There is a big gulf between the activists on the ground and the ones outside Syria,” said Fawaz A. Gerges, professor of Middle Eastern politics at the London School of Economics. Both Assad and his opponents, he said, are “realizing this is going to be a prolonged, complex, bloody struggle.”

Despite Annan’s six-point plan, international pressure on Assad is minimal, Gerges added, because neither Annan nor an Arab League summit in Baghdad this week have explicitly called on the Syrian president to step down, and his allies remain supportive. In Lebanon on Friday, the influential leader of Hezbollah, Hassan Nasrallah, reiterated his support for the Syrian authorities in a televised speech.

“Neither Assad nor the opposition really believes that Annan’s plan will go anywhere,” Gerges said. The opposition has been increasingly using guerrilla tactics such as bombings and ambushes, he said, causing civilian casualties as well as striking security forces. Meanwhile, he said, Syrian soldiers have been moving further into urban areas.

“Annan’s plan is an absolute and pure waste of time,” said Ausama Monajed, a spokesman for the largest coalition of opposition groups, the Syrian National Council.

Some countries, notably Qatar and Saudi Arabia, have indicated that they already support armed rebels, while other nations, especially Syria’s neighbors Iraq and Turkey, fear that further militarizing the chaotic uprising could create far-reaching regional conflict.

“The main task now is to organize the opposition, creating a chain of command and a structure that is going to be effective,” Monajed said. “Otherwise, you’re throwing millions at it without knowing where it is going.”