This post is part of our special coverage Yemen Protests 2011.

A teenager was shot and killed in Aden, Yemen on Monday, February 21 as tens of thousands of demonstrators gathered in four separate cities on the 11th day of protests calling for the end of the three-decade reign of President Ali Abdullah Saleh. At least 11 people have died since the demonstrations began, and Amnesty International says at least 78 people have been injured. Five students remain in police custody.

In a press conference on Monday, President Saleh said he refused to step down, but did offer to hold talks with opposition parties. This was quickly rejected. The protesters, younger citizens and opposition party supporters, don't appear to be going anywhere soon. Students began camping out at Sana'a University on Sunday. And in Aden, police fired warning shots to disperse protesters, who also said they would make a camp.

Al-Masdar Online has photos from Monday's rallies.

Video photographers grabbed shots from all over the country.

This video, uploaded by Mualla district of Aden hurling a photo of the president over a balcony.

This is a video of a February 21 protest in a district of Aden, uploaded by Diaz9th

A video, uploaded by yemen5100 shows an anti-government demonstration.

People inside and outside Yemen were also active on Twitter.

@yemen4change: It's very inspiring to hear citizens from #Ibb & #Abyan provinces showing solidarity by joining pro-change demonstrators in Liberty Square in #Taiz #Yemen

@Yemen_2011 #Yemen -some friends in Sanaa who spoke of support 4 #Egypt #Tunisia hv nw fully joined protesters – Yemenis walk da talk – many new faces

@dia_assada: Right now in Freedom Square, Taiz, #Yemen, all the protesters are praying in one voice for saving their brothers n sisters in #Libya

@AlaaIsam links to a photo of a demonstration of Northern Works in Sailah market in Saana's crater district.

The photo is here.

@ma2moun: By the way, Ali Abdullah Saleh, if you are watching and trying to learn fro Gaddafi u better not, ur people have tanks, leave now #Yemen

@nayemkabir: That bastion of truth, Hillary Clinton has spoken out against the tyrant Gaddafi but still stands firm with her friends in Yemen & Morocco.

This post is part of our special coverage Yemen Protests 2011.