Henry Purdy crosses for Gloucester against Zebre© Stu Forster/Getty Images

Champions Gloucester started their European Challenge Cup defence with a 23-10 victory against Zebre, on a weekend when all five European ties in France were cancelled due to Friday's terror attacks in Paris.

All of Gloucester's points came in the first-half as tries from Henry Purdy, Ross Moriarty and Steve McColl plus eight points from the boot of Billy Burns put the home side in control.

Lewis Ludlow was shown a yellow card shortly after the break and the visitors were quick to make their advantage count. A 51st-minute penalty try was converted by Edoardo Padovani to give the Italian side hope, before the fly-half's successful penalty had the Kingsholm crowd on edge.

However, with Ludlow back on the field, Gloucester held on for an opening-day win in Pool 4.

Sean Maitland crosses for London Irish against Agen© Ben Hoskins/Getty Images

London Irish hammered Agen 48-10 in their opening Pool 5 match, scoring eight tries to earn a bonus point win.

The visitors took the lead at the Madejski Stadium through a Francois Bouvier penalty, but it would not be long before the Exiles took firm control.

Gerard Ellis crossed twice in the first half, with Johnny Williams and Joe Treyfoot also scoring as the hosts established a 24-3 halftime lead.

Rob McCusker and Sean Maitland grounded within three minutes of each other, in between a second-half double from Alex Lewington. Chris Noakes added eight more points from the kicking tee, with Felicien Vergnon scoring the only try for Agen.

Cardiff Blues began their European campaign with a seven-try, bonus point triumph over Italian side Calvisano -- their first win since the opening weekend of the Guinness PRO12.

Tries from Lloyd Williams -- celebrating his 100th appearance -- and Tom James, plus five points from the boot of Rhys Patchell, gave the away side a comfortable lead at the break.

Five of Cardiff's tries came in the second period, with Ellis Jenkins, Dan Fish, Blaine Scully, Gavin Evans and a penalty try making sure the Blues made a perfect start to this season's competition.

Patchell added a further six points with three conversions, taking his personal tally to 11 points, while Jarrod Evans stepped up to successfully convert two tries in the last 10 minutes.

Filippo Buscema kicked three penalties for the hosts, who never looked like winning. Cardiff now face a five-day turnaround before they host fellow Pool 3 opponents Harlequins.

Worcester Warriors and La Rochelle observe a minutes silence© Tony Marshall/Getty Images

Ryan Lamb kicked 14 points as Worcester Warriors got off to a winning start against Stade Rochelais in Pool 4.

Four penalties from Lamb gave the hosts a 12-3 lead at the break, with Charles Bouldoire on target for the French side.

And it would not be until the 77th minute until the next points came; Ben Howard was set free to cross over before Lamb converted for a 19-3 win.

Connacht picked up a bonus-point 31-14 win against RC Enisei, who became the first Russian side to feature in European competition.

Two AJ MaGinty penalties gave the Irish side a 6-0 lead at halftime in what were bitterly cold conditions in Siberia -- Connacht's replacements were all tucked under several blankets on the bench.

However, second-half tries from Niyi Adeolokun, John Muldoon and Darragh Leader -- combined with another MacGinty penalty and conversion from Leader -- secured victory in Pool 1.

Andrei Polivalov had the 4,000 home supporters cheering, though, as he crossed over twice in the final 10 minutes, both of which were converted by Yuri Kushnarev to add gloss to the scoreline.