Students opposed to Venezuela's government have returned to the streets to protest against President Nicolas Maduro after a week of violence that saw three people killed at political rallies.
Hundreds of protesters assembled in Caracas, blocking a main highway into the capital. Security forces fired tear gas and water cannon to try to disperse the crowd.
The tension that surrounds the demonstrations in the city was underscored by a report from Twitter that the government has blocked pictures of the unrest from being shared between users on the micro-blogging service.
The state-owned telecommunications company CANTV "emphatically" denied putting any such restrictions in place.
The anti-government movement was launched 10 days ago by students who have received backing from some of the country's fractured opposition groups, the AFP news agency reported.
Rampant crime, soaring inflation and basic goods shortages are their main grievances.
The past week has seen the biggest show of defiance to Maduro's leadership since he took over from the late Hugo Chavez last year.
"We are here once again to demand the release of students who were detained and because we can't live with such violence," Maria Correia, 20, said in a wealthy neighbourhood in the eastern section of Caracas.
'No more violence'
Under a hot sun, the young protesters gathered near Plaza Altamira, wearing the national flag on their backs and brandishing signs that read "We are all Venezuela, peace for students" and "We want peace, no more violence."
Other protests took place across the country, including in the western city of San Cristobal.
The protesters have demanded that Maduro step down, but main opposition leader Henrique Capriles has said the political conditions are not favourable to the president's exit, AFP reported.
Maduro has called a demonstration by his supporters "for peace and against fascism" on Saturday.
The dueling processions follow a fierce opposition demonstration in Caracas on Wednesday in which a pro-government demonstrator and two students died.
Dozens more were wounded and many were arrested.
Expressing concern at the growing unrest, the UN High Commissioner for Human Rights and the Organisation of American States have demanded explanations about the events.
Foreign media manipulation
Most Venezuelan television channels have abstained from covering the unrest of recent days, after the National Telecommunications Council media regulator warned of sanctions against outlets that "encourage violence".
In remarks late on Thursday, Maduro accused foreign media, including the AFP news agency, of manipulating coverage of the unrest, and took Colombian 24-hour cable news channel NTN24 off the air.
On Friday, Twitter provided advice on how to sidestep a block on pictures being shared on the network - instructing
Venezuelan users to have tweets delivered to smartphones in text messages.
Maduro has also ordered the arrest of a senior opposition figure and declared that he would not be overthrown, though protesters say a coup is not their goal.
Wednesday's violence led to a security crackdown in cities across a country where the economy has been battered by inflation of more than 50 percent.
Venezuela, whose government is dependent on oil revenues for its state-led system, has been hurt by a shortage of hard currency, while dwindling supplies of consumer goods have frustrated even some government supporters.
The government blames 'bourgeois' local business interests for trying to profit from its largely low- and middle-income political base.