Serbian President Aleksandar Vucic on Sunday denied that Belgrade had masterminded a strike on Kosovar infrastructure, saying Kosovo itself had mounted a "hybrid attack" against his country.
The strike late on Friday -- near the town of Zubin Potok in an area of Kosovo's volatile north dominated by ethnic Serbs -- damaged a canal supplying water to hundreds of thousands of people and cooling systems at two coal-fired power plants that generate most of Kosovo's electricity.
Kosovar Prime Minister Albin Kurti immediately accused Serbia of masterminding the blast, calling the incident a "terrorist attack".
Serbia's Vucic fired back in an address to the nation on Sunday, saying the incident and the accusations by Pristina were "an attempt at a large and ferocious hybrid attack" on Serbia itself.
Belgrade's Kosovo office said the strike gave the government in Pristina an excuse to crack down on ethnic Serbs in Kosovo.
"We have no connection with it," Vucic said of the attack.
He stopped short of directly accusing any individual or state of orchestrating the blast and said Serbian authorities had launched their own separate investigation into the incident.
The explosion has sent tensions soaring between the two arch rivals, with both sides trading accusations.
Petar Petkovic, the director of the Serbian government's Kosovo office, said the incident provided Kosovar Prime Minister Kurti with a pretext to try and expel ethnic Serbs from northern Kosovo.
"What happened in the village of Varage gave Kurti an alibi to continue the attacks in the north of Kosovo... and to continue the policy of expulsion of the Serb people," Petkovic told public broadcaster RTS.
On Sunday, Kosovo officials brought in measures to better protect critical infrastructure, with police and security forces conducting patrols.
"The Security Council has approved additional measures to strengthen security around critical facilities and services such as bridges, transformer stations, antennas, lakes, canals, etcetera," the government said.
It said it was also stepping up cooperation between its governing institutions, and with international bodies, "to prevent similar attacks in future".
On Saturday, Kosovar authorities arrested several suspects.
Police chief Gazmend Hoxha said that his office had seized "200 military uniforms, six grenade launchers, two rifles, a pistol, masks and knives" in the operation.
Animosity between Serbia and Kosovo, which has an ethnic Albanian majority, has persisted since the end of the war between Belgrade's forces and ethnic Albania separatists in what was then a province of Serbia in the late 1990s.
Kosovo declared independence in 2008, a move that Serbia has never acknowledged.
Kurti's government in Pristina has for months sought to dismantle a parallel system, backed by Belgrade, that provides social services and political offices for Kosovo's ethnic Serb minority.
Friday's attack followed a series of violent incidents in northern Kosovo, including one in which hand grenades were hurled at a local council building and a police station earlier this week.
Kosovo is due to hold parliamentary elections on February 9.
