* Police, militants clash near Algerian border
* Ansar al-Sharia blamed for attacks
* Islamist-led government under pressure over security
TUNIS, Oct 18 (Reuters) - Tunisian police killed two Islamist militants and arrested others from the hardline group Ansar al-Sharia after two policemen were killed in fighting near the Algerian border, a senior security source said on Friday.
The source, who asked not to be identified, said the clashes had occurred on Thursday in the northeastern city of Goubellat.
Ansar al-Sharia is the most radical Islamist group to emerge in Tunisia since the 2011 uprising that ousted autocrat Zine al-Abidine Ben Ali and inspired Arab revolts elsewhere.
Interior Minister Lotfi Ben Jedou told state television the gunmen who had been killed or arrested were linked to Ansar al-Sharia, which authorities say is affiliated with al Qaeda's North African wing.
Tunisia's government, led by moderate Islamist party Ennahda in coalition with two smaller secular parties, is under pressure to tackle security threats from Islamist militants to help safeguard the North African country's democratic transition.
Ennahda responded two months ago by declaring Ansar al-Sharia a terrorist organisation and accusing it of carrying out the assassinations of two secular opposition leaders this year.
The killings of secular opposition politicians Chokri Belaid and Mohamed Brahmi provoked the biggest opposition street protests in Tunisia since the overthrow of Ben Ali in 2011.
Since its revolt, Tunisia has seen mounting strife over the political role of Islam between secularists who long held power and Islamists whose influence is increasing in one of the most secular countries in the Muslim world.
Salafi Islamists have prevented concerts and plays staged in several Tunisian cities, declaring they violated Islamic principles. Hardline Islamists also ransacked the U.S. embassy a year ago during worldwide Muslim protests over an Internet video they said insulted the Prophet Mohammad. (Reporting by Tarek Amara; editing by Patrick Markey and Alistair Lyon)