Complex sentence: On 5 April, the Jaysh al-Islam, claimed that its fighters were refused access to the camp by al-Nusra Front and that al-Nusra allowed ISIL to enter the camp, which led to some defections from the first party.
Split into simpler sentences: On 5 April, the Jaysh al-Islam, claimed that its fighters were refused access to the camp by al-Nusra Front. It also claimed that al-Nusra Front allowed ISIL to enter the camp, which led to some defections from the first party.