Thailand's military has suspended the country's 2007 constitution and imposed a country-wide curfew just hours after dismissing the caretaker government in a coup d'etat.

The curfew is to last from 2200 to 0500 while the suspension of the constitution is a temporary measure, a military spokesman said.

In other drastic steps, Thai radio and television networks will only be allowed to broadcast military material while public gatherings of more than five people are now banned.

"All radio and television stations, satellite and cable, must stop normal programming and broadcast army content until told otherwise," deputy army spokesman Winthai Suvaree said in a televised statement.

Political turmoil has blighted the southeast Asian nation for six months after former prime minister Yingluck Shinawatra -- sister of deposed former prime minister Thaksin Shinawatra -- dissolved the lower house of the Thai parliament last year.

Thailand's army chief general Prayuth Chan-ocha said in a televised statement that the military took control of the country's government to "restore order and push through political reform" after two days of failed talks between Thailand's main political factions.

"We are concerned that this violence could harm the country's security in general," he said after declaring martial law.

"In order to restore law and order to the country, we have declared martial law. I'm asking all those activist groups to stop all activities and cooperate with us in seeking a way out of this crisis."

The anti-government movement is opposed to the involvement of anyone associated with Yingluck's brother Thaksin who was removed from office in 2006.

An interim prime minister, Niwattumrong Boonsongpaisan, was installed earlier this month after a court ordered Yingluck's removal for abuse of power.

The military's coup of the interim government is the country's 19th takeover in 82 years.