As sporting rivalries go, few carry as much passion and fervor as a soccer match between Glasgow clubs Rangers and Celtic.
But ancient divisions in Scotland's largest city run much deeper than allegiance to the clubs known collectively as the "Old Firm." Soccer is more than just a passing hobby here as support is drawn along deep religious and sectarian divides.
That conflict came to the fore Wednesday with news that parcel bombs had been sent to Celtic manager Neil Lennon and two prominent club supporters. The devices were intercepted before they reached their intended targets.
"They were definitely capable of causing significant harm and injury to individuals if they had opened them," Detective Chief Superintendent John Mitchell of Strathclyde police said.
While police didn't discuss the motive behind the mail bombs, sectarian tensions in both Northern Ireland and in Glasgow are regularly played out between Celtic fans, who are mostly Catholic, and Rangers fans, who are mostly Protestant.
"We are fans of the most tribal clubs in the world — the outside world has to understand that," Dennis O'Neil, a 44-year-old Celtic fan, said Wednesday outside the club's Celtic Park stadium. "But this takes it too far."
At Ibrox, home to Rangers, 28-year-old David McIver said: "This is not happening in my name. This is probably just one crazy man doing this."
Strathclyde Police have reported increases in domestic violence after Old Firm games and said in the last two years 2,400 crimes could be connected to the matches, including attempted murders, riots and assaults on emergency workers.
The current season is one of the closest in years, with both clubs fighting for the Scottish Premier League title. The next matchup comes on Easter Sunday, the seventh and final Old Firm clash of the season, and authorities are hoping the game will be remembered for the right reasons.
Tom Devine, a historian at Edinburgh University who has advised the Scottish government on sectarianism, believes the mail bomb campaign could prove a turning point in authorities' desire to tackle the problem.
"This level of violence is totally unprecedented in Scottish and European football (soccer) and it should concentrate the minds of the authorities," he said. "We may witness a watershed, where at last the authorities such as the police and judiciary actually use the laws we have in place to deal with offenders."
He called attempted bombings "a humiliation for the Scots, who see their prime virtue as being a country of the Scottish Enlightenment. This is the country of David Hume and Adam Smith, not this form of bigotry."
Lennon, a Catholic and former Northern Ireland international, has been the focus of previous hate campaigns by Rangers fans, first as a player at the club and then as manager. He quit international soccer in 2002 after claiming he had received death threats from a paramilitary group in Northern Ireland.
In early March, Lennon and Rangers counterpart Ally McCoist had to be separated after they clashed on the pitch at the end of an Old Firm game.
Scotland First Minister Alex Salmond called a summit of the two clubs and police in an effort to calm the atmosphere. But Strathclyde Police revealed on Wednesday that, just two days after that match, the first parcel bomb to Lennon was intercepted at a Royal Mail sorting office in Saltcoats, Ayrshire, about 33 miles (53 kilometers) south of Glasgow.
Since then, Lennon's lawyer Paul McBride and Celtic-supporting lawmaker Trish Godman were also targeted by mail bombs.
Salmond described those responsible as "a lunatic element."
Amid both sets of fans are extremists who sport flags and banners supporting paramilitary groups in Northern Ireland such as the Real IRA and the Ulster Volunteer Force.
Rangers wouldn't sign Catholic players or staff until Mo Johnston, a former Celtic player, crossed the divide and joined the club in 1989. He was vilified and hailed a hero in equal measure during his two-year stint.
UEFA, European soccer's governing body, recently announced two charges against Rangers for sectarian chanting by its fans at Europa League matches against the Dutch club PSV Eindhoven.
Devine believes the current crisis is the result of greater integration of Irish Catholics into Scottish society.
"Ironically, we now have a burgeoning new Irish Catholic middle class, many of whom are probably not even churchgoers, but are no longer prepared to keep their heads below the parapet like their forebears," he said.
"This is not just about religious groupings, it is also tribal and semi-ethnic," Devine said.
Since the touchline clash in early March, Lennon and McCoist have sought to stress cordial relations between the clubs.
McCoist, who played for Scotland and appears regularly on TV quiz shows, said Rangers and Celtic staff regularly socialize with each other and their wives and girlfriends.
"If that bomb was intended to inflict pain and damage on people, then it is an evil act and should be dealt with in the right way," he said.
Peter Lawwell, the chief executive of Celtic, said in a statement: "It is an intolerable state of affairs which must end. We enjoy friendship and respect throughout the world yet, here in Scotland, we are caught up in these vile events."