The four were arrested on Wednesday and remanded in police custody pending further investigation before the prosecution issued its detention order, Kuwait Human Rights News Centre said on its Twitter account.
Three other Twitter users, including a woman, who were arrested with them were each freed on bail of $3 550.
The seven, described as opposition sympathisers, were interrogated on allegations of tweets deemed offensive and critical of Emir Sheikh Sabah al-Ahmad al-Sabah.
The clampdown on users of the social network was strongly criticised by opposition figures, with Hamad al-Matar, a member of the scrapped 2012 parliament, saying Kuwait was becoming a "police state".
Last week, the emirate's secret service police detained for two days two members of the Al-Sabah ruling family on accusations of writing tweets deemed offensive to the emir. Several former opposition MPs and activists are facing trial over similar charges.
Public criticism of the ruler is illegal under the Kuwaiti constitution. Kuwait has plunged into a deep political crisis after the government amended the electoral law ahead of the December 1 general election which the opposition has decided to boycott.
The Islamist, nationalist and liberal opposition has been staging street protests in which about 150 protesters and 24 police were slightly wounded. It plans more protests and is urging voters to shun the ballot. – Sapa-AFP