Lille coach Christophe Galtier was emotional after his team's Europa League game against Celtic on Thursday, saying that France is "bruised" following a "cowardly" knife attack in Nice.
Three people were killed in a Nice church earlier on Thursday in what President Emmanuel Macron said was an "Islamist terrorist attack".
"France is bruised... France is bruised," said Galtier.
"Even if it is not much, I want to offer my condolences to the friends, to the families, to the relatives of the people who were cowardly murdered today in a church. Two women, one man...
"Believe me, it was a difficult day on a personal level. If I could have avoided working, I would have done."
A 21-year-old Tunisian migrant, who had a copy of the Koran and three knives with him, shouted "Allahu Akbar" (God is Greatest) when approached by police who shot and seriously wounded him, France's anti-terror prosecutor Jean-Francois Ricard told a press conference.
"Apart from the health crisis, to live such moments in our beautiful country, believe me that it is very difficult," added Galtier, with France to reenter lockdown on Friday in an attempt to slow the spread of coronavirus.
"And once again, I reiterate all my support to the relatives of the cowardly murdered people and to the people of Nice. It's a city that is often the target of attacks."
Nice has been attacked by terrorists before, including in July 2016 when 86 people were killed.
Lille drew their Europa League group game with Celtic 2-2.