(Adds comment by U.S. State Department, paragraphs 8-9)
DUBAI, Jan 7 (Reuters) - A Kuwaiti court sentenced a man to two years in prison on Monday for insulting the country's ruler on Twitter, his lawyer said, the second person to be jailed for the offence in as many days.
The U.S.-allied Gulf Arab state has clamped down in recent months on political activists who have been using social media websites to criticise the government and the ruling family.
Kuwait has seen a series of opposition-organised protests, including one on Sunday night, since the ruling emir, Sheikh Sabah al-Ahmad al-Sabah, used emergency powers in October to change the voting system.
The court sentenced Ayyad al-Harbi, who has more than 13,000 followers on Twitter, to the prison term two months after his arrest and release on bail.
Harbi used his Twitter account to criticise the Kuwait government and the emir. He tweeted on Sunday: "Tomorrow morning is my trial's verdict on charges of slander against the emir, spreading of false news."
His lawyer, Mohammed al-Humidi, said Harbi would appeal.
"We've been taken by surprise because Kuwait has always been known internationally and in the Arab world as a democracy-loving country," Humidi told Reuters. "People are used to democracy, but suddenly we see the constitution being undermined."
On Sunday, another man, Rashid Saleh al-Anzi was given two years in prison over a tweet that "stabbed the rights and powers of the emir", according to the online newspaper Alaan. Anzi, who has 5,700 Twitter followers, was expected to appeal.
In Washington, the U.S. State Department said it had seen the reports of the two men's sentences and had raised the issue with the Kuwaiti government, which it urged to respect freedom of speech.
"We call on the government of Kuwait to adhere to its tradition of respect for freedom of assembly, association, and expression," State Department spokeswoman Victoria Nuland told reporters. "You know how strongly we feel about locking people up for their use of Twitter."
Kuwait, a major oil producer, has been taking a firmer line on politically sensitive comments aired on the Internet.
In June 2012, a man was sentenced to 10 years in prison after he was convicted of endangering state security by insulting the Prophet Mohammad and the Sunni Muslim rulers of Saudi Arabia and Bahrain on social media.
Two months later, authorities detained Sheikh Meshaal al-Malik Al-Sabah, a member of the ruling family, over remarks on Twitter in which he accused authorities of corruption and called for political reform, a rights activist said.
Public demonstrations about local issues are common in Kuwait, a state that allows the most dissent in the Gulf, and the country has avoided Arab Spring-style mass unrest that has ousted four veteran Arab dictators in the past two years.
But tensions have risen between Kuwait's hand-picked government, in which ruling family members hold the top posts, and the elected parliament and opposition groups. (Reporting by Mahmoud Habboush; additional reporting by Arshad Mohammed in Washington; Editing by Mark Heinrich and David Brunnstrom)