* No claim of responsibility for attack on base

* Base located near Aden's international airport

* Islamic State in Yemen has carried out similar attacks

(updates death toll, adds children killed)

By Mohammed Mukhashaf

ADEN, July 6 (Reuters) - At least six Yemeni troops and around 20 militant attackers were killed on Wednesday in an assault on a military base near the international airport of Yemen's southern city of Aden, security sources said.

The assault began when two suicide bombers blew up their cars, followed by armed militants storming the Solaban base. They occupied several buildings but were killed after four hours of heavy gun battles, the sources said.

There was no immediate claim of responsibility but Islamic State carried out a similar large-scale attack in the southern port of Mukalla on June 27.

In recent days there has also been a raft of bombings apparently carried out by Islamic State in Saudi Arabia, Turkey, Bangladesh and Iraq.

The surge in violence coincided with the last days of the Islamic holy month of Ramadan when Muslims fast from dawn until dusk. Wednesday marked the beginning of Eid al-Fitr, a major religious festival.

In the past year, Islamist militants in Yemen have gained in territory and freedom to operate from a civil war pitting government forces against Iran-allied Houthi rebels. The Houthis control the capital, Sanaa.

Both Al Qaeda and Islamic State operate in Yemen. The groups consider government forces and the Houthis as enemies, but are otherwise ideological rivals and compete for recruits.

Al Qaeda has used the security vacuum to seize control over swathes of southern and eastern Yemen. Islamic State has launched several attacks on security forces.

Three coordinated Islamic State bomb attacks on government troops killed 38 people in Mukalla on June 27 as they were preparing to break their Ramadan fast.

In a separate incident on Tuesday night, a Katyusha rocket barrage launched by Houthi forces on the outskirts of the central city of Marib killed seven children between the ages of five and nine, local officials said.

A shaky ceasefire that began nearly three months ago has paused a civil war which started when the Houthis pushed the government into exile in March 2015. But clashes regularly flare on various battlefronts throughout Yemen.

The conflict has killed over 6,400 people - around half of them civilians, according to the United Nations - and plunged the impoverished country into a humanitarian crisis.

(Reporting By Mohammed Mukhashaf and Mohamed Ghobari; Writing by Noah Browning; Editing by Robert Birsel and Raissa Kasolowsky) ((noah.browning@thomsonreuters.com;))