PRISTINA (Reuters) - Kosovo warned on Friday of possible attacks against senior politicians and Kosovan institutions during the Easter holiday, a day after the U.S. Embassy in Pristina alerted its citizens to the risk of violence.

There were increased police patrols on the capital’s streets and two officers told Reuters their shifts had been extended to 12 hours from the usual eight for the next few days.

The government gave no details about who was plotting the potential attacks.

“Groups have planned to commit (violent) acts against some institutional and political leaders of Kosovo,” the government said in a statement.

Kosovo is grappling with the threat posed by Kosovars loyal to Islamic state. A total of 300 Kosovars went to Syria to fight alongside Islamic State and local and international intelligence agencies are concerned about those returning home from combat zones.

In November, police in Kosovo arrested 19 people on suspicion of having links with Islamic State and planning attacks.

Those behind the attack threats “may be linked with people already incriminated in the conflicts outside Kosovo and also with some particular countries aiming to destabilize Kosovo,” the government statement said.

In its notice, the U.S. Embassy said that “terrorists in the region have previously sought to attack soft targets” such as churches, shopping malls and sports arenas.

Kosovo declared independence from Serbia in 2008 with the backing of the West and relations between the two remain strained. In 2015, Pristina adopted a law introducing jail terms of up to 15 years for anyone convicted of fighting in wars abroad.