Four suspected militants have reportedly been arrested in Libya in connection with the death of U.S. Ambassador to Libya Chris Stevens and three other consulate employees.

Stevens and the three others were killed when armed militants overran the consulate during a protest over an anti-Islamic video defaming the Muslim Prophet Muhammad. Officials say they believe the attack on the consulate was planned in advance, however, and may have been unrelated to the protest over the video.

The attack came on the same day as protesters overran the U.S. Embassy in Cairo, Egypt. The protest in Egypt was over the same video.

Security was increased today at U.S. embassies around the world. An elite group of Marines have been sent to Libya to reinforce security there, while the Pentagon is moving two warships to the Libyan coast.

Protesters today also began to lay siege to the U.S. Embassy in Yemen. Employees of the embassy in Yemen are being removed from the compound and taken to somewhere safe.