Syrian activists say government shelling and gunfire killed at least nine people across the country on Wednesday, most of them in a region where U.N. military observers were caught up in a deadly shooting and bomb blast the day before.

The Britain-based Syrian Observatory for Human Rights said security forces opened fire in the northwestern town of Khan Sheikhoun, killing five people a day after at least 20 mourners were shot dead at a funeral procession.

Six U.N. monitors who were visiting the town at the time of Tuesday's incident left on Wednesday after spending the night with opposition activists who said they were protecting the foreigners. The U.N. team's convoy was struck by a roadside bomb shortly after the Tuesday shootings, but none of the observers were hurt. It was not clear who caused the blast.

U.N. mission chief Robert Mood, a Norwegian general, said Wednesday the monitors told him they were well-treated and were heading back to base. He expressed gratitude to the Syrian government for “facilitating” the observers departure from Khan Sheikhoun.

The U.N. personnel are part of a larger group of observers who have deployed across Syria to assess government and rebel compliance with a fragile April truce brokered by international mediator Kofi Annan.

In other violence, the Observatory said government troops killed three people at a refugee camp in the southern province of Daraa and a fourth person in a shelling attack in the central Homs region. The rights group said another 15 civilians had been executed in Homs city since Tuesday. None of the casualties could be independently confirmed.

Syrian President Bashar al-Assad said Wednesday that his forces have captured and killed an undisclosed number of foreign mercenaries as part of a crackdown on a 14-month opposition uprising. In his first interview in six months, Mr. Assad told the Russia-24 television channel that his government is “preparing to show (the mercenaries) to the world.”

The Syrian president has long-accused foreign-backed terrorists of driving the revolt against his 11-year rule. The uprising began with peaceful pro-democracy protests but became increasingly militarized as Syrian rebels began to fight back against security forces who attacked protesters.

Mr. Assad also accused U.N. personnel in Syria of unfairly criticizing violent actions by government forces and ignoring attacks by terrorists. He said he will raise the complaint with Mr. Annan later this month, when he said the international envoy will visit the country.

In another part of his interview with the Russian state-run network, the Syrian president said the participation of Syrians in a parliamentary election earlier this month shows they support the political reforms he has introduced to address the country's uprising. Russia is a key military ally of Mr. Assad and has supported his reform pledges.

Syria said the election drew a 51 percent turnout, but opposition groups boycotted the vote and said few people cast ballots in rebellious towns and cities across the country.

Farhan Haq, a spokesman for U.N. Secretary-General Ban Ki-moon, told Alhurra television that continued violence in Syria indicates that both sides need to uphold the provisions of Mr. Annan's framework for peace.

“They need to abide by that agreement. They need to cease all violence and we are going to do what we can to calm the situation down and press both sides to do just that.”

Middle East analyst Nadim Shehadi says incidents such as the Tuesday blast near a U.N. convoy will eventually hamper the work of the monitors.

“It is certain that them being targeted will affect their mission. They will not be able to conduct their mission and they will be subject to more manipulation by the regime for security reasons.”

The United Nations says more than 9,000 people have been killed in violence related to the anti-government uprising that erupted more than a year ago. The Syrian government has blamed armed terrorist groups for much of the country's unrest.